Pressor doses of norepinephrine (NE) (n = 8) and angiotensin II (A II) (n = 5) were infused in normal volunteers to determine whether the systemic administration of vasopressor hormones influence renal eicosanoid production and whether, in turn, the eicosanoids produced could modulate renal hemodynamics and electrolyte excretion. At the doses administered, both pressor substances induced the expected rise in blood pressure, a significant decrease (P less than 0.05) in renal blood flow and a proportionally smaller fall in glomerular filtration rate, resulting in a consistent augmentation in filtration fraction. Fractional sodium excretion was concomitantly reduced. NE infusion produced only slight modifications in urinary prostaglandin (PG)E2, 2,3-dinor-6-keto-PGF1 alpha and thromboxane (TX)B2, while urinary 6-keto-PGF1 alpha and PGF2 alpha were increased by 38% and 176% respectively. The increase in urinary 6-keto-PGF1 alpha (the non-enzymatic degradation product of PGI2, predominantly of cortical origin) was proportional to the level of circulating NE (r = 0.78, P less than 0.05) and to the renal vascular resistance (r = 0.85, P less than 0.01), suggesting an immediate compensatory role for PGI2 in response to the NE-induced pressor stimulus. The renal production of PGE2 and PGF2 alpha (predominantly medullary) was inversely correlated with the filtration fraction: the greater the increase in PGE2 and PGF2 alpha the lower the elevation in filtration fraction or the decline in renal blood flow upon NE administration. All infusion variably stimulated the renal eicosanoid production: PGE2, 41%; PGF2 alpha, 102%; 6-keto-PGF1 alpha, 38%; 2,3-dinor-6-keto-PGF1 alpha, 38%; and TXB2, 25%.(ABSTRACT TRUNCATED AT 250 WORDS)

Chronic renal failure (CRF) is a progressive disease with severe pruritus and dry skin as the major symptoms. However, the mechanisms of CRF-induced pruritus remain unclear. In this study, 5/6 nephrectomized (NPCT) mice were used as a mouse model of CRF. Serum concentrations of blood urea nitrogen and creatinine in 5/6 NPCT mice were increased. The stratum corneum water content in the skin of 5/6 NPCT mice was decreased. These findings suggest that 5/6 nephrectomy in mice results in a phenotype resembling human CRF. 5/6 NPCT mice showed spontaneous scratching, which was inhibited by μ-opioid receptor antagonist, suggesting that the scratching is an itch-related response. The number of cutaneous mast cells was not altered in 5/6 NPCT mice compared with sham-operated mice. The H₁ histamine-receptor antagonist, proteinase-activated receptor 2-neutralizing antibody, and 5-HT₃-receptor antagonist did not inhibit spontaneous scratching in 5/6 NPCT mice; therefore, the role of mast cells and serotonin in spontaneous scratching appears to be minimal. The anti-allergy agent azelastine, BLT leukotriene (LT) B₄ receptor antagonist, and TP thromboxane (TX) A₂ receptor antagonist inhibited spontaneous scratching in 5/6 NPCT mice, suggesting that LTB₄ and TXA₂ are involved in CRF-induced pruritus. Interestingly, in the skin of 5/6 NPCT mice, levels of two newly identified pruritogens (β2-microglobulin and interleukin-31) were increased. Taken together, these findings suggest that 5/6 NPCT mice are useful for the study of itching in CRF. In addition to LTB₄ and TXA₂, it is also suggested that β2-microglobulin and interleukin-31 are involved in itching associated with CRF-induced pruritus.

The mode of action of rat interferon (IFN) on growth of the R3230AC mammary adenocarcinoma was studied in vivo in Fischer female rats. A dose of 1 X 10(4) units of rat IFN given thrice weekly inhibited the growth of the transplanted mammary tumors. Of the five eicosanoids measured in the tumor, the content of four arachidonate products, prostaglandin (PG) E2, PGF2 alpha, 6-keto-PGF1 alpha, and thromboxane (TX) B2, was higher in mammary tumors from IFN-treated rats than the control rats. PGE2 was the major eicosanoid. In vitro PG synthesis (PGE1, PGE2, and PGF2 alpha) was lower in tumor microsomes prepared from IFN-treated tumors. These data suggest that the tumor content of four arachidonate products in the IFN-treated tumors was related to the in vivo effects of rat IFN. Indomethacin, a cyclooxygenase inhibitor, also inhibited tumor growth. Furthermore, when indomethacin was administered daily in combination with rat IFN, the tumor-inhibiting effect of rat IFN was reduced. These observations suggest that the effects of eicosanoids appear to be biphasic in this tumor model. Inhibition of arachidonic acid metabolism resulted in tumor growth inhibition, a finding consistent with the view that eicosanoid production is required for tumor enhancement. Conversely, in the experiments with rat IFN, retardation of tumor growth is associated with a greater amount of arachidonic acid metabolism, and indomethacin prevents this effect. Eicosanoids appear to be required for tumor-inhibiting effects of rat IFN, and yet inhibition in vivo of eicosanoid synthesis also resulted in retardation of tumor growth. Although the precise mechanism of action in each situation is unclear, these apparently contradicting results are consistent with the biphasic actions of eicosanoids reported in some normal tissues and transformed tumor cell lines.

The role of arachidonic acid in patients with acute myocardial infarction (AMI) was investigated. Plasma levels of thromboxane (TX) B2, 6-keto-prostaglandin F1 alpha (6KPG), leukotriene (LT) B4, LTC4, peptideLTs (LTC4 + LTD4 + LTE4) were evaluated in 19 AMI patients, 2 unstable angina (UA) patients and 12 normal controls. Blood samples were obtained from the femoral and pulmonary arteries. Further, plasma levels of LTC4 from the antecubital vein were determined in 14 AMI patients on admission and 10 healthy volunteers. Plasma levels of TXB2, LTB4, LTC4, peptideLTs from arterial blood significantly increased in AMI patients at the acute stage and one day after an attack of AMI compared with those of normal controls. TXB2, LTB4, LTC4, peptideLTs levels in UA patients were higher than those of normal controls. TXB2, LTC4 and peptideLTs levels on week after an attack of AMI significantly decreased compared with those at the acute stage, and these values decreased to normal control levels one month after an attack of AMI. LTB4 levels did not decrease one week after an attack of AMI but they significantly decreased one month after an attack compared with those at the acute stage. These values from the pulmonary artery were not significantly different from the values from the femoral artery obtained at the equivalent phases. Plasma levels of 6KPG did not show significant serial changes either. But the patients showing high levels of 6KPG in the acute stage showed lower levels of CPK and lower Wanger's QRS score than the patients showing low levels of 6KPG. Plasma LTC4 levels in the venous blood of 14 AMI patients were also significantly higher than those of healthy volunteers. Serum levels of lipid peroxide, alpha-tocopherol and superoxide dismutase activity were also measured but did not show significant serial changes in AMI patients. These results in AMI patients suggest that LTB4, LTC4 and peptideLTs, which are lipoxygenase metabolites of arachidonic acid, play an important role in the pathogenesis of AMI attacks as well as TXB2 and 6KPG, which are cyclooxygenase metabolites of arachidonic acid.

In both pyrogen-induced fever and fever subsequent to acute hypothalamic trauma, pyrexia is believed to be mediated by cyclooxygenase products acting within the anterior hypothalamic/preoptic (AH/PO) region of the brain. The goal of the present study was to assess, through a potency analysis, the likely contributions of various prostanoids to pyrexia production. Prostanoids and prostanoid-mimetics were injected bilaterally into the AH/PO region of conscious, indomethacin pretreated cats, and partial dose-response curves for pyrexic activity were obtained. ED1 degrees doses (doses producing a 1 degree C fever) for PGE2, PGE1 and 6-keto-PGE1 (a metabolite of PGI2 and/or of the PGI2 hydrolysis product, 6-keto-PGF1 alpha) ranged between 2 and 15 pmol. PGF2 alpha and the stable PGI2-mimetics, iloprost and 6-beta-PGI1, required doses of 900-1100 pmol. PGD2 and 6-keto-PGF1 alpha had ED1 degrees doses of 2200-2400 pmol. PGI2, thromboxane (TX) B2 and the TXA2/PGH2-mimetics, SQ26655, 9,11-azo-PGH2 and U46619, were incapable of producing a 1 degrees C rise at the maximum dose of 30,000 pmol. The results offer no support for an involvement in fever of PGF2 alpha, PGD2, TXA2, TXB2, PGH2, PGI2 or 6-keto-PGF1 alpha. Only the 3 E-series prostaglandins were sufficiently potent to merit serious consideration as mediators of pyrexia. Of these, only PGE2 is known to be produced in abundance by cat brain; no information is available regarding PGE1 production, and our results with PGI2 and 6-keto-PGF1 alpha indicate that cat brain may not synthesize 6-keto-PGE1. The results thus suggest an important role for PGE2 in fever production in the cat and are compatible with an involvement of PGE1.

OBJECTIVE

The authors investigated prostacyclin (PGI2) and thromboxane (TX) productions in peripheral venous blood after lower limb revascularization by percutaneous transluminal angioplasty (PTA) versus diagnostic angiography. The purpose of this study was to investigate PGI2/TX imbalance after PTA. This imbalance is of pathophysiologic importance and it is a potential sign of platelet function alteration.

METHODS

Twenty-five patients requiring PTA were compared with 20 patients undergoing angiography alone from April 2004-December 2005 from a single vascular unit. Patient age range was 42-90 years, and the majority of patients were men. Prostaglandin F2-alpha (PGF2-alpha) and thromboxane B2 (TXB2) were measured sequentially (preprocedure, at 1 hour, and 24 hours after procedure). Differences between postprocedure and preprocedure level were compared statistically between angiography and PTA.

RESULTS

Baseline demographics were distributed equally between the two groups except presence of critical ischemia and ankle brachial pressure index, which were two significant confounders. TXB2 was significantly higher after PTA at 1 hour and 24 hours after PTA (P = .005 and P = .014 respectively), PGF2-alpha was significantly higher 24 hours after PTA only (P = .018) (Mann-Whitney U test).

CONCLUSIONS

PGI2/TX balance homeostasis is of significant pathophysiologic importance. The authors found that PTA results in significant PGI2/TX imbalance and shifts more toward increased TX production. This finding is partly suggestive of significant platelet activation. This imbalance in PGI2/TX level may have implications for future failure of PTA. Future research in reducing this platelet activation is recommended.

(1) Fructose (F) overload produces elevated blood pressure (BP), hyperglycaemia, hypertriglyceridemia and insulin resistance, resembling human metabolic syndrome. Previously, we found altered vascular prostanoid (PR) production in this model. (2) Sodium molybdate (Mo), as well as sodium tungstate, causes insulin-like effects and normalizes plasma glucose levels in streptozotocin-treated diabetic rats. We studied the effects of Mo on BP, metabolic parameters and release of PR from the mesenteric vascular bed (MVB) in F-overloaded rats. (3) Four groups of male Sprague-Dawley rats were analysed: Control, tap water to drink; F, F solution 10% W/V to drink; CMo, Mo 100 mg kg day(-1) and FMo, both treatments. After 9 weeks, the animals were killed and MVBs removed and the released PRs measured. (4) F increased BP, glycemia, triglyceridemia and insulinemia. Mo treatment prevented the increases in BP and glycemia, but did not modify triglyceridemia or insulinemia. In addition, Mo decreased BP in controls. (5) Prostaglandins (PG) F2 alpha and E2, PG 6-ketoF1 alpha and thromboxane (TX) B2 , as well as inactive metabolites of prostacyclin (PGI2 ) and TXA2 were detected. F decreased the production of vasodilator PRs PGI2 and PGE2 in MVB. Mo prevented these alterations and increased PGE2 in controls. Vasoconstrict or PRs PGF2 alpha and TXA2 release was not modified. (6) Mo treatment, beyond its known lowering effect on glycemia, prevents the reduction in the vascular release of vasodilator PR observed in this model. This could be one of the mechanisms by which Mo avoids the increase in BP caused by F overload in the rat.

Effects of endotoxin on arachidonic acid (AA)-induced hepatic glycogenolysis were examined in perfused rat liver. In normal rat liver, infusion of AA increased oxygen consumption and glucose production concurrently. In rats injected with lipopolysaccharide (LPS) 6 h before, AA increased glucose production but suppressed oxygen consumption. The changes in LPS-injected rat were abolished by a thromboxane (Tx) A2 receptor antagonist. The release of Tx B2 by AA increased after LPS-injection. These results suggest that priming of hepatic macrophage by endotoxin in vivo enhances Tx synthesis, resulting in modulating hepatic glycogenolysis.

Our group has previously shown that αB-crystallin (HSPB5), a small heat shock protein, inhibits human platelet aggregation by ristocetin, an activator of glycoprotein Ib/IX/V. In addition, it was demonstrated that glycoprotein Ib/IX/V activation induces soluble CD40 (sCD40) ligand release via thromboxane (TX) A2. In the present study, the effect of αB-crystallin on the ristocetin-induced sCD40 ligand release in human platelets was investigated. The ristocetin-induced release of sCD40 ligand was suppressed by αB-crystallin. In addition, αB-crystallin reduced the ristocetin-stimulated production of 11-dehydro-TX B2, a stable metabolite of TXA2. αB-crystallin did not suppress the platelet aggregation induced by U46619, a TXA2 receptor agonist. αB-crystallin had little effect on the U46619-induced phosphorylation of p38 mitogen-activated protein kinase or sCD40 ligand release. In addition, αB-crystallin failed to reduce the binding of SZ2, a monoclonal antibody against the sulfated sequence in the α-chain of glycoprotein Ib, to the ristocetin-stimulated platelets. These results strongly suggest that αB-crystallin extracellularly suppresses ristocetin-stimulated release of sCD40 ligand by inhibiting the TXA2 production in human platelets.

1. ATP, bradykinin (BK), and A-23187 activated the generation of prostaglandin (PG) E2 and thromboxane (TX) B2 in rabbit astrocytes, but not in human astrocytoma cells (1321N1). 2. In human astrocytoma cells, ATP, BK, and A-23187 could not release [3H]arachidonic acid (AA) from [3H]AA-labeled cells and exogenous AA was not converted to TXB2 and PGE2, suggesting the lack of phospholipase (PL) A2 and cyclooxygenase activities in 1321N1 human astrocytoma cells, although they express TXA2 receptors. 3. In rabbit astrocytes, ATP and BK, but not A-23187, showed increased accumulation of inositol phosphates, indicating that an increase in intracellular Ca2+ concentration alone would not be enough to activate PLC. Furthermore, indomethacin, a cyclooxygenase inhibitor, partially attenuated ATP-induced phosphoinositide hydrolysis, indicating that cyclooxygenase product(s) would secondarily activate PLC in response to ATP.

We have previously demonstrated that catecholamines have opposite effects on leukotriene (LT) and prostanoid synthesis. The aim of the present study was to test the effects of phenols (catechol, hydroquinone, phenol and resorcinol) on LTB4, LTE4 and thromboxane (TX)B2 synthesis in A23187-stimulated human whole blood. All tested compounds inhibited LTB4 and LTE4 synthesis. The IC50 values for catechol were 3 microM, 6 microM; for hydroquinone 4 microM, 3 microM; for phenol 285 microM, 226 microM and for resorcinol 180 microM, 902 microM. The compounds did not stimulate TXB2 synthesis but only inhibited it. The IC50 value for catechol was 3 microM, for hydroquinone 7 microM, for phenol 18 microM and for resorcinol 25 microM. Catechol and hydroquinone had hardly any effect on the LT/TX ratio. Phenol and resorcinol even increased the LT/TX ratio. The positions of hydroxyl groups of phenolic compounds are thus important for their actions on the LT/TX ratio.

To study the role of thromboxane (Tx) A2 in Forssman systemic shock (FSS) in guinea pig, the effect of (E)-3-[p-(1H-Imidazol-1-ylmethyl)phenyl]-2-propenoic acid hydrochloride (OKY-046), a specific Tx A2 synthetase inhibitor, was studied. OKY-046 administered intravenously clearly prolonged survival time and protected against fatal shock. In shocked animals, definite decreases in serum complement hemolytic activity (CH50), leucocyte counts and platelet counts and an increase in lactate dehydrogenase (LDH) activity were observed. In addition, a significant increase of Tx B2 and incoagulability of blood were observed after shock. Whereas OKY-046 had no effect on the decreases in CH50, platelet counts and leucocyte counts, it inhibited the increase of Tx B2 and increased the amount of 6-keto PG F1 alpha. When Forssman antibody (half a lethal dose) was injected, a diphasic increase in airway resistance was observed. OKY-046 inhibited this diphasic increase in airway resistance. These data suggest a pathophysiological role for Tx A2 in FSS. OKY-046 inhibited the Forssman antibody induced respiratory disorders probably due to the inhibition of Tx A2 synthesis after shock.

Thromboxane (TX) B2, a stable metabolic product of hydrolysis of TXA2, was measured by radioimmunoassay in tissue extracts of ovaries of immature rats pretreated with pregnant mare's serum gonadotropin and human chorionic gonadotropin. Ovarian concentrations of TXB2 increased before, and remained elevated after, the time of ovulation. In a subsequent study, ovulation was inhibited in a dose-dependent fashion by a reported TXA2 receptor antagonist, AH23848. Nevertheless, inhibition of the preovulatory rise in synthesis of TXB2 by furegrelate (a thromboxane synthetase inhibitor) did not prevent ovulation. Nor was the blockade of ovulation caused by indomethacin (a cyclooxygenase inhibitor) reversed by a TXA2 mimetic (U-46619). It does not appear that a preovulatory increase in ovarian thromboxane is an obligatory component of the ovulatory mechanism of gonadotropin-primed immature rats.

We examined effects of small dose (1 microM or less) of exogenous 12-hydroperoxy-5,8,10,14-eicosatetraenoic acid (12-HPETE) on the formation of cyclooxygenase products from exogenous arachidonic acid (AA) in washed human platelets. With a simultaneous addition of AA, 12-HPETE did not affect the formation of thromboxane (TX)B2 and 12-hydroxy-5,8,10-heptadecatrienoic acid (HHT). However, by being preincubated with platelets before an addition of AA, 0.1 microM or greater of 12-HPETE inhibited the formation of TXB2 and HHT dose-dependently. In addition, the inhibitory effect of 12-HPETE increased as the preincubation time was prolonged. These results suggest that 12-HPETE is a strong inhibitor for the cyclooxygenase pathway.

Although intracoronary administration of the complement component, C5a, produces deleterious effects on regional coronary blood flow and segmental ventricular function, it is unclear whether a direct myocardial action contributes to the dysfunction induced by the anaphylatoxin. We therefore evaluated the effects of purified porcine C5a on contractile tension of isolated supported ventricular trabeculae from pig hearts. Muscles were studied in a myograph bath at 30 degrees C, electrically stimulated 12 times per minute, and stretched to produce maximal isometric developed tension. C5a concentrations of 30, 100, and 300 ng/ml increased tension (P less than 0.05) 9.8, 5.5, and 20.9%, respectively. In seven of nine muscles exposed to 300 ng/ml C5a, tension initially decreased 10.5% (P less than 0.05) before the positive inotropic effect. Tachyphylaxis was demonstrated by lack of contractile response to a second administration of C5a greater than 70 min after the initial exposure to the complement fragment. Blockade of histamine H1 receptors with diphenhydramine (10(-6) M) markedly attenuated both the positive and negative contractile responses to C5a. beta-Adrenoceptor blockade with propranolol (5.6 x 10(-7) M) did not alter the response to C5a. Levels of thromboxane (Tx)B2, the stable metabolite of TxA2, were augmented in the bath after exposure to C5a (59 +/- 27.3 to 104 +/- 28.2 pg/ml, P less than 0.05). Although the TxA2 agonist, U-46619 (50 ng/ml), significantly increased tension, TxA2 receptor blockade with SQ 29548 (50 ng/ml) did not alter the response to C5a.(ABSTRACT TRUNCATED AT 250 WORDS)

We infused noradrenaline (0.025 micrograms/kg/min for 60 min, n=7) and dopamine (3.0 micrograms/kg/min for 60 min, n=6) into healthy male volunteers to study the effects of these catecholamines on in vivo thromboxane A2, prostacyclin and leukotriene E4 production measured as urinary excretions of 11-dehydro-thromboxane (TX) B2, 2,3-dinor-6-keto-prostaglandin (PG) F1alpha and leukotriene (LT) E4, respectively. Plasma noradrenaline and dopamine concentrations were 2.9+/-0.3 and 233+/-17 nmol/l at the endo fo the noradrenaline and dopamine infusions, respectively. Noradrenaline decreased thromboxane production and increased leukotriene production almost two fold. It had hardly any effect on prostacyclin production. Dopamine had no significant effects on any of the variables, however, it had a tendency to increase prostacyclin and leukotriene production. The results indicate that noradrenaline is a more important modulator of arachidonic acid metabolism than dopamine in vivo.

1. In order to assess the effects of atrial natriuretic factor on the renal biosynthesis of prostaglandins (PG), the urinary excretion of PGE2, PGF2 alpha, 6-keto-PGF1 alpha and thromboxane (Tx)B2 were followed in eight salt-loaded healthy volunteers infused for 2 h with a non hypotensive dose of human atrial natriuretic peptide (hANP, 0.7 nmol min-1). 2. Within 1 h, hANP, infusion produced a marked increase in the urinary PG output, especially of PGE2 and 6-keto-PGF1 alpha (188 +/- 21% and 202 +/- 24% of the pre-infusion values respectively), followed by a significant decrease during the recovery period. 3. No correlations could be uncovered between the urinary excretion of sodium and that of any of the PGs. In contrast, during the infusion of hANP, the urinary output of PGE2 and of 6-keto-PGF1 alpha was found positively related to the urinary flow rate (r = 0.42; P less than 0.05; n = 32 and r = 0.43; P less than 0.05; n = 32 respectively) as well as during the recovery period (r = 0.66, P less than 0.001; n = 32 and r = 0.55; P less than 0.01; n = 32 respectively). 4. It was concluded that, in man, infusion of a non hypotensive dose of hANP is followed by a rise in urinary PG excretion presumably reflecting enhanced renal PG biosynthesis. This increased urinary PG excretion does not seem to be involved in the natriuretic action of hANP but might participate to its diuretic effect.

The gas chromatographic (GC) and GC-mass spectrometric properties of the diethylhydrogensilyl-cyclic diethylsilylene (DEHS-DES) derivatives of prostaglandin (PG) F1 alpha methyl ester, PGF2 alpha methyl ester, 6-keto-PGF1 alpha methyl ester-alkyloxime and thromboxane (TX) B2 methyl ester-alkyloxime and the DES derivative of 13,14-dihydro-15-keto-PGF2 alpha methyl ester-alkyloxime were studied. When the ketonic PGs and TXB2 were converted into their methyloxime derivatives, the methylene unit values of these five prostanoid derivatives were slightly greater than those of the corresponding dimethylethylsilyl ether derivatives. When the ketonic PGs were converted into their corresponding ethyloxime derivatives, baseline separation was achieved in 20 min by use of a methylsilicone cross-linked fused-silica capillary column. The mass spectra of these derivatives were characterized by the ion at m/z 157 for F alpha prostaglandins and m/z 269 for TXB2. The major fragmentations were directed by the DES group, and other fragmentations common to the prostanoid derivatives were losses of an ethyl radical at the silicon atom, C5H11 hydrocarbon fragment, diethylhydrogensilanol and C15-C20 hydrocarbon fragment. The mass fragmentations of these prostanoid derivatives are briefly discussed. GC with high-resolution selected-ion monitoring was carried out for the TXB2 derivative at a resolution of 8000 by monitoring the ion at m/z 269.1573. A 25-pg amount of this derivative showed a well shaped doublet with a signal-to-noise ratio of more than 300:1.

The present study was designed to clarify the possible role of renal prostaglandins (PGs) on blood pressure (BP) regulation during calcium (Ca) restriction or supplementation. Twelve normotensive women with a mean age of 21.2 years participated in the study. After 1 week of normal Ca intake (mean +/- SE, 536 +/- 2 mg/day), a low-Ca diet (163 +/- 1 mg/day) was given for a further 1 week. Additional asparagine Ca (3 g as Ca/day) was also given to half of the subjects. BP, heart rate, and serum total and ionized Ca concentrations were measured at the end of each period. Levels of Ca, sodium, PGE2, 6-keto-PGF1 alpha and thromboxane (TX) B2 excreted into urine were also determined. The plasma level of ionized Ca was significantly increased without any change in total Ca in both groups. Low and high Ca intake decreased and increased urinary Ca excretion by 28% and 56%, respectively. BP was not altered after Ca deprivation or loading. However, urinary PGE2 excretion was significantly augmented from 668.9 +/- 68.1 to 959.7 +/- 183.1 ng/day by Ca loading, whereas Ca deprivation decreased PGE2 excretion (695.4 +/- 108.1 to 513.2 +/- 55.2 ng/day). No changes were observed in 6-keto-PGF1 alpha or TXB2 urinary excretion. These results suggest that renal PGE2 synthesis is stimulated or decreased by 1-week Ca loading or deprivation, indicating a possible antihypertensive role of renal PGE2 during high-Ca intake in hypertensives.

The role of endogenous prostaglandins in the modulation of lower oesophageal sphincter (LES) function has been assessed by giving three structurally unrelated cyclooxygenase inhibitors and monitoring their acute effects on LES tonus and platelet thromboxane (TX) B2 production in 20 healthy volunteers. In a double-blind, placebo-controlled, cross-over study, IV injection of soluble salts of acetylsalicylic acid and indomethacin elicited a transient increase in LES tonus of approximately 50% over baseline. A similar pattern was observed after the rectal administration of indomethacin. In contrast, indoprofen had no measurable effect on LES tones, despite comparable inhibition of platelet cyclooxygenase activity. This may have been due to the markedly different tissue distribution of the drug. The results suggest that endogenous prostaglandins physiologically exert an inhibitory influence on LES function.

The hairpin conformational hypothesis has been proposed to rationalise much of the structure-activity and receptor-binding data which have accumulated for the prostaglandin (PG) hormones. The hairpin conformation, thought to be necessary for PG activity, requires that the alpha- and omega-chains of the molecule be extended and in parallel alignment, separated by a van der Waals contact distance for the full length of the chains, with the ends of the chains approximately 5.5 A apart. The similarity between the structures of the thromboxanes (TXs) and the PGs suggests that the profile of activity of TXs, like that of PGs, centres on subtle conformational variation of the hairpin geometry. Thromboxane B2 (TXB2) is a stable hydrolysis product of a highly reactive, short-lived intermediate, thromboxane A2 (TXA2), which is formed from the prostaglandin endoperoxide (PGH2) as indicated in Fig. 1. An examination of molecular models of TXA2 and TXB2 suggests that the structural differences between the ring moieties may have much less influence in altering the side-chain conformation of TXs than do substitutents on the relatively more flexible cyclopentane ring of a PG molecule. We report here the first diffraction analysis of a thromboxane structure and note that the molecular conformation is not hairpin shaped.

Exogenous prostaglandins (PGs) have been shown to have differing effects on frog lung contractility. In this study, prostaglandin synthesis was measured in lung tissues from warm-acclimated (WA, 22 degrees C) and cold-acclimated (CA, 5 degrees C) American bullfrogs, Rana catesbeiana, incubated for 30 min at 5 degrees or 22 degrees C. Media were assayed by radioimmunoassay for PGE2, PGF2 alpha, 6-keto PGF 1 alpha (the metabolite of PGI2), and thromboxane (TX)B2 (the metabolite of TXA2). PGE2 was produced in greatest quantity by tissues from WA and CA animals, at both incubation temperatures. Epinephrine stimulated PGE2, PGF2 alpha, and TXB2 synthesis at 22 degrees C but only stimulated PGE2 production at 5 degrees C. In tissues from CA frogs, epinephrine did not stimulate prostaglandin synthesis at either incubation temperature. Ibuprofen (10(-5) M) inhibited basal and epinephrine-stimulated prostaglandin synthesis in tissues from WA frogs incubated at 22 degrees C. The beta receptor antagonist propranolol (10(-6) M) blocked the epinephrine-stimulated synthesis of PGE2, PGF2 alpha and TXB2, suggesting epinephrine stimulates prostaglandin synthesis through beta receptor activation. The absence of stimulation by epinephrine in lung from CA animals, but not in 5 degrees C incubations of tissues from WA animals, suggests that a modification of beta receptors occurs during prolonged cold exposure.

To evaluate the roles of interleukin-1 (IL-1) in regulation of ovarian prostaglandin (PG) synthesis, we examined the effects of IL-1 beta on PGE2, PGE2 alpha, 6-keto-PGF 1 alpha and thromboxane (TX) B2 synthesis in cultures of human ovarian granulosa cells. Granulosa cells were obtained from hyperstimulated follicles in patients undergoing oocyte retrieval for in vitro fertilization-embryo transfer (IVF-ET). IL-1 beta increased immunoreactive concentrations of PGE2 and PGF2 alpha in culture medium in time- and dose-dependent manners. Concentration of PGE2 was significantly higher after 24 h incubation with 5 or more units/ml of IL-1 beta, when compared to the control value obtained without IL-1 beta (P < 0.05). Concentration of PGF2 alpha was significantly higher after 8 h incubation with more than 2 units/ml of IL-1 beta (P < 0.05). The increase in PGE2 was observed even in the presence of human chorionic gonadotropin (hCG), and blocked by indomethacin, an inhibitor of cyclooxygenase. During a 10 day incubation period, stimulatory effects of IL-1 beta on PG synthesis were observed only on the first 2 days incubations. Concentrations of 6-keto-PGF 1 alpha and TXB2 were below our measurement limits. This study demonstrated that IL-1 beta stimulates PG synthesis in human ovarian granulosa cells in vitro. IL-1 seems to play an important role in regulating ovarian functions.

The present experiments describe the study of the metabolism of 14C-arachidonic acid and the effect of exogenous norepinephrine (NE) on prostanoid production in the anterior preoptic area and medial basal hypothalamus (APOA-MBH) of prepubertal (16 days of age) and peripubertal female rats (30 days old). Four prostanoids were produced from 14C-arachidonic acid (6-keto-prostaglandin(PG)F1 alpha, PGF2 alpha, PGE2 and thromboxane (TX)B2) and were released to the incubating medium. The basal percent of conversion was not significantly different between them. In prepubertal rats the addition of NE (10(-5) M) to the medium did not modify on the synthesis of these eicosanoids. In peripubertal rats there are no significant differences in the basal production of 6-keto-PGF1 alpha, PGF2 alpha, PGE2 and TXB2 as compared to prepubertal rats. Moreover, the percentage of conversion of arachidonic acid into the different prostanoids was similar in prepubertal and peripubertal hypothalamus. Nevertheless, when NE (10(-5) M) was added to the incubation medium of peripubertal hypothalamus. Nevertheless, significant increase in the synthesis of PGE2 was observed (control: 1.75 +/- 0.1; NE 2.90 +/- 0.3; p < 0.01). This increase in the synthesis was not accompanied by changes in the synthesis of any of the other three prostanoids. Prazosin, a well-known alpha 1-receptor adrenoblocker at a dose of 10(-5) M did not modify the production of 6-keto-PGF1 alpha, PGF2 alpha, PGE2 and TXB2 but did induce a complete inhibition of the stimulation by NE of PGE2 synthesis (NE: 2.85 +/- 0.1; prazosin: 1.9 +/- 0.09; p < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)