Increased urinary metabolites of the antiaggregatory vasodilator prostacyclin (PGI2) and the proaggregatory vasoconstrictor thromboxane A2 (TXA2) have been reported in deep vein thrombosis; however, the tissue(s) of origin is uncertain. Because little is known about the formation of PGI2 or TXA2 from its common precursor, prostaglandin (PG) endoperoxide H2 (PGH2), by varicose veins, we determined the formation of 6-keto-PGF1 alpha (the stable metabolite of PGI2), TXB2 (the stable metabolite of TXA2), and PGE2. Segments of normal saphenous vein and varicose vein (nine and six patients, respectively) were incubated with 10 microM [14C]PGH2 for 2 min at 37 degrees C; products were separated by thin-layer chromatography. Surface area and mass of normal and varicose vascular segments were 19.5 +/- 0.8 versus 18.8 +/- 0.6 mm2 and 11.6 +/- 1.4 versus 10.7 +/- 0.7 mg, respectively. Formation of 6-keto-PGF1 alpha and TXB2 by the segments of varicose vein was significantly increased over that of normal vein: 157 +/- 14 versus 243 +/- 17 pmole of 6-keto-PGF1 alpha (P less than 0.005) and 22 +/- 3 versus 35 +/- 5 pmole of TXB2 (P less than 0.01). The formation of PGE2 by segments of varicose vein was not significantly different from that of normal vein (201 +/- 9 vs 219 +/- 11, respectively). Deoxyribonucleic acid (DNA) content of normal and varicose vein was 1.69 +/- 0.12 and 1.51 +/- 0.13 mg per gram of tissue, respectively. The data suggest that the increased PGI2 formation may reflect increased activity or content of PGI2 synthase. The increase in TXA2 formation may reflect increased productivity or an increased presence of residual platelets or microemboli.

Lipocalin-type prostaglandin (PG) D synthase (L-PGDS) is a multi functional protein acting as a PGD(2) synthesizing enzyme, a transporter or scavenger of various lipophilic ligands, and an amyloid β chaperon in the brain. L-PGDS is a member of the lipocalin superfamily and has the ability to bind various lipophilic molecules such as prostanoid, retinoid, bile pigment, and amyloid β peptide. However, the molecular mechanism for a wide variety of ligand binding has not been well understood. In this study, we determined by NMR the structure of recombinant mouse L-PGDS and L-PGDS/PGH(2) analog complex. L-PGDS has the typical lipocalin fold, consisting of an eight-stranded β-barrel and a long α-helix. The interior of the barrel formed a hydrophobic cavity opening to the upper end of the barrel, the size of which was larger than those of other lipocalins and the cavity contained two pockets. Kinetic studies and molecular docking studies based on the result of NMR titration experiments provide the direct evidence for two binding sites for PGH(2) and retinoic acid in the large cavity of L-PGDS. Structural comparison of L-PGDS/U-46619 complex with apo-L-PGDS showed that the H2-helix, CD-loop, and EF-loop located at the upper end of the β-barrel change the conformation to cover the entry of the cavity upon U-46619 binding. These results indicated that the two binding sites in the large cavity and induced fit mechanism were responsible for the broad ligand specificity of L-PGDS.

We have characterized the thromboxane (TX) A2/prostaglandin (PG) H2 receptor in glomeruli isolated from the rat using the agonist radioligand [125I]-BOP. Binding of [125I]-BOP was highly specific, stereoselective, and to a single class of high affinity binding sites (Kd = 1.16 +/- 0.22 nM and Bmax = 348 +/- 32 fmol/mg protein; n = 6). Binding of [125I]-BOP was competed for by the agonist ONO11113 (Kd = 50.8 +/- 8.0 nM; n = 4) and the antagonists SQ29548 (Kd = 15.8 +/- 1.0 nM; n = 3), L657925 (Kd = 12.1 +/- 2.2 nM; n = 3) and L657926 (Kd = 1642 +/- 135 nM; n = 3). I-BOP also produced a TXA2/PGH2 receptor-mediated rise in [Ca2+]i in isolated glomeruli In adriamycin-induced nephrotic syndrome in the rat, the development of proteinuria is reported to be dependent on increased renal TXA2 production. We therefore examined whether or not changes in glomerular TXA2/PGH2 receptors occur between control and nephrotic rats. No changes in expression or affinity of either glomerular or platelet TXA2/PGH2 receptors were observed. Kd and Bmax values for isolated glomeruli were 1.45 +/- 0.24 nM and 406 +/- 72 fmol/mg for controls and 1.22 +/- 0.25 nM and 321 +/- 62 fmol/mg for nephrotic rats (n = 6).

In isolated and enriched guinea-pig gastric mucous cells the effects of carbachol, prostaglandin E2 (PG E2), prostaglandin F2 alpha (PG F2 alpha) and histamine on adenylate cyclase (AC) and cytosolic free Ca2+ were investigated, in order to study the biochemical mechanisms involved in secretagogue-mediated mucus release. Histamine and both prostaglandins stimulated AC in partially purified membranes of mucous cells. Histamine was most efficacious, followed by PG E2 and PG F2 alpha. The histamine effect was blocked by the H2-receptor antagonist ranitidine, but not by the H1-receptor antagonist mepyramine. Carbachol raised the resting [Ca2+]i in mucous cells from 120 to 306 nM. This carbachol effect was blocked by atropine. Histamine and PG E2 stimulation of AC was inhibited in a concentration-dependent manner by Ca2+ (IC50:31 microM). In the presence of TPA and phosphatidylserine, conditions which activate protein kinase C, the inhibitory action of Ca2+ on AC was significantly increased. These data indicate that there exists a negative feedback control mechanism between protein kinase C and histamine/prostaglandin E2-induced AC activation. From the finding that TPA and phosphatidylserine increased the inhibitory action of Ca2+ on cholera toxin-, but not on forskolin-stimulated AC we assume that the point, where protein kinase C exerts its inhibitory effect at the AC, is the guanine nucleotide regulatory protein.

After discovery of H. pylori, management of peptic ulcer disease (PUD) is getting much easier. However, four thousands a year still died caused by this disease in Japan. Ten to twenty percent of the non-NSAIDs ulcer could be expected to remain after complete eradication of H. pylori; The number could be still 100,000-200,000 a year in Japan. Furthermore, NSAIDs ulcer would not decrease in number in the post-H. pylori era. Recurrence of ulcer is related to the quality of ulcer healing. Deficiency of prostaglandins(PG) in the mucosa is another main reason than H. pylori infection of poor quality of ulcer healing. Therefore, a PG analogue may be a most reasonable tool for treatment of H. pylori-negative PUD including NSAIDs ulcer, but is often poorly tolerated because of diarrhea and abdominal pain. The mucosal damage caused by NSAIDs is also gastric acid-dependent and so, an H2-receptor antagonist is to some extent effective although the efficacy is far behind of that with a PG-analogue. Recently, a proton-pump inhibitor has been reported to exert the same effect as a PG-analogue in healing of gastroduodenal mucosal damage caused by NSAIDs and the superior effect in preventing recurrence of the damage with better tolerance. This results suggest that strong acid inhibition is highly effective for such damage. Whether such strong acid inhibition causes disturbance of absorption of NSAIDs is not clear, which might result in poor antiinflammatory effect. Elderly patients often have tendency of constipation and less possibility of pregnancy. Therefore, a PG-analogue may be not only safe but also more favorable for such patients.

A new method based on high-performance liquid chromatography (HPLC) coupled with on-line gold nanoparticle-catalyzed luminol chemiluminescence (CL) detection was developed for the simultaneous quantitation of catecholamines in rat brain. In the present CL system, gold nanoparticles were produced by the on-line reaction of H2 O2 , NaHCO3 -Na2 CO3 (buffer solution of luminol) and HAuCl4. Norepinephrine (NE), epinephrine (EP) and dopamine (DA) could strongly enhance the CL signal of the on-line gold nanoparticle-catalyzed luminol system. The UV-visible absorption spectra and transmission electron microscopy studies were carried out, and the CL enhancement mechanism was proposed. Catecholamines promoted the on-line formation of more gold nanoparticles, which better catalyzed the luminol-H2 O2 CL reaction. The good separation of NE, EP and DA was achieved with isocratic elution using a mixture of methanol and 0.2% aqueous phosphoric acid (5:95, v/v) within 8.5 min. Under the optimized conditions, the detection limits, defined as a signal-to-noise ratio of 3, were in the range of 1.32-1.90 ng/mL, corresponding to 26.4-38.0 pg for 20 μL sample injection. The recoveries of catecholamines added to rat brain sample were >94.6%, with the precisions <5.5%. The validated HPLC-CL method was successfully applied to determine NE and DA in rat brain without prior sample purification.

1. The role of endogenous nitric oxide (NO) and prostaglandins (PGs) in the gastric mucosal protective action of pibutidine hydrochloride (IT-066), a novel histamine H2-receptor antagonist, was investigated in a 0.15 N hydrochloride (HCl) + 60% ethanol (EtOH)-induced gastric lesion model. 2. The 0.15 N HCl + 60% EtOH-induced lesion formation was reduced significantly by IT-066 (3 mg/kg, PO), NOR3 (spontaneous NO releaser; 0.03-0.1 mg/kg, SC) or PGE2 (0.01 mg/kg, PO) but was not reduced by famotidine (1-10 mg/kg, PO). 3. Pretreatment with NG-nitro-L-arginine methyl ester (L-NAME) (3 mg/kg, IV), an inhibitor of NO synthase, inhibited the protective action of IT-066 (3 mg/kg, PO), and the inhibitory effect of L-NAME was reversed by L-arginine (300 mg/kg, IV). The protective effect of PGE2 (0.01 mg/kg, PO) was not affected by the pretreatment with L-NAME (3 mg/kg, IV). 4. Infusion of carboxy-PTIO (1 mg/kg/min), a direct NO scavenger, inhibited the protective effect of IT-066 (3 mg/kg, SC) or NOR3 (0.1 mg/kg, SC). Pretreatment with indomethacin (5 mg/kg, SC) markedly reduced the protective effect of IT-066 (3 mg/kg, PO) or NOR3 (0.1 mg/kg, SC). 5. These results suggest that endogenous NO and PGs may be implicated in the gastric mucosal protection induced by IT-066 and that the endogenous PGs may contribute to the protective effect of NO.

Among H2-receptor antagonist (H2RA)-refractory ulcers, non-responders that did not heal after 5 months therapy had high intraluminal pH in the basal condition and high sensitivity to inhibition of acid secretion by H2RA but possessed gastric mucosa to generate less prostaglandins. Combination therapy of PGE1-analogue with H2RA healed these ulcers by 60%. Proton-pump inhibitor (PPI) exerted a complete inhibition of acid secretion in these patients and the rate of healing was 88%. Helicobacter pylori was present in the mucosa of all 4 ulcer patients refractory to treatment with PPI. The ulcers healed in 3 out of 4 patients after eradication of H. pylori. It is suggested that PG supplement or complete inhibition of acid secretion is effective for ulcers in H2RA-non-responders. PPI-refractory ulcers may relate to H. pylori infection.

A solid sampling method for the determination of lead in foods (including grains, vegetables and seafoods) using electrothermal vaporization atomic fluorescence spectrometry was established. The method introduced samples using electrothermal vaporization by quartz furnace and used on-line ashing and vaporization to remove matrix interferences for the specific trap of lead. It was proven by the certified reference material (CRM) and the recovery rate of the standards that the electrothermal vaporization was stable and there was no effect for sampling difference. The best operating program and parameters for the new method included ashing (850°C, 160 s), vaporization and trap (1050°C, 80 s; 800°C, 10 s), release (800°C, 10 s), and mixed Ar + H2 (85:15%, v/v) as carrier gas with flow rate of 500 mL/min. The relative standard deviations of repeated Pb measurements in CRMs were all below 5.0%, and the recovery rate ranged from 90.0 - 110.0%. The limit of detection (LOD) for the new method was 3.0 pg and the limit of quantification (LOQ) was 10.0 pg. The total time of analysis was less than 6 min. No significant differences existed between the results measured by the new method and microwave ICP-MS.

Neurohistochemical and in vivo and electron microscopic methods demonstrated alpha-and beta-adrenergic receptors and adrenergic innervation in arterioles and "arterial" capillaries of the mouse spleen. Such innervation and receptors in venules and channels within the red pulp were sparse. Cholinergic innervation and receptors were judged to be absent in the microvasculature. Histamine elicited arteriolar dilation which was blocked by metiamide suggesting the presence of H2 receptors. However, following blockade of H2 receptors, histamine produced arteriolar constriction. Serotonin elicited only venular constriction. Lactic acid caused arteriolar constriction; bradykinin and prostaglandins (PG) E2 and PGF2 alpha triggered arteriolar constriction, but only at higher concentrations. The vasoconstriction evoked by cholinergic agonists, histamine, lactic acid, or PGs was partially or completely antagonized by alpha-adrenoceptor blockade or by reserpine, and the vasoconstrictor responses to histamine, lactic acid, PGs, bradykinin were enhanced in the presence of functional adrenergic nerves. In the latter case higher doses of phentolamine provoked arteriolar vasospasm. Although adenine nucleotides, guanosine, inosine, sodium phosphate, and sodium chloride elicited no response, adenosine was a potent vasodilator. This dilation was not blocked by beta-adrenergic antagonists, and it was enhanced in the presence of functional adrenergic nerves. The data suggest that: (1) cholinergic agonists, lactic acid, histamine, and PGE2 and PGF2 alpha cause alpha-mediated arteriolar constriction by releasing stored neurotransmitter(s) from splenic nerves, and (2) subthreshold quantities of neurotransmitter(s) may modulate microvascular sensitivity to vasoactive agents which act directly upon the vascular wall.

This study was undertaken to evaluate the effects of acute pressure overload on prostacyclin (PGI2) release and the influences of 15-hydroperoxy-eicosatetraenoic acid (15-HPETE), an inhibitor of PGI2 synthetase, and indomethacin, an inhibitor of cyclo-oxygenase, in canine hearts. Gradual stenosis of the ascending aorta was performed in 24 anesthetized open-chest dogs. The mongrel dogs were divided into three groups, which received indomethacin, 15-HPETE, and no drug. Changes in the hemodynamics, regional myocardial blood flow (MBF) by the method of H2 gas clearance, and plasma immunoreactive 6-keto-prostaglandin (PG) F1 alpha level in the descending aorta (AO) and great cardiac vein (GCV) were measured. Five minutes after aortic stenosis, the plasma immunoreactive 6-keto-PGF1 alpha level in the GCV and MBF increased from 162 +/- 23 to 289 +/- 37 pg/ml and from 87 +/- 5 to 107 +/- 8 ml/min/100 g, respectively, and the calculated coronary vascular resistance (CVR) decreased significantly from 0.93 +/- 0.08 to 0.77 +/- 0.08 mmHg/ml/min/100 g. These significant changes persisted thereafter. Continuous infusion of 15-HPETE (66 pg/kg/min) into the coronary artery simultaneously prevented significant changes in MBF and the plasma immunoreactive 6-keto-PGF1 alpha level in the GCV and CVR. Intravenous infusion of indomethacin (5 mg/kg), on the other hand, induced a significant decrease in the plasma immunoreactive 6-keto-PGF1 alpha level in both the GCV and AO; significant changes in MBF 5 to 15 min after aortic stenosis and CVR were not affected. From these results, it is suggested that PGI2 plays an important role in the regulation of coronary blood flow in canine hearts with acute pressure overload.(ABSTRACT TRUNCATED AT 250 WORDS)

A bleached sulfate integrated pulp and paper mill producing printing and writing paper from mixed tropical hardwood and bamboo was studied. The mill uses a "conventional bleaching sequence," C-E-H1-H2, with an average molecular chlorine consumption of 50 kg per ton of air-dried pulp (ADP). The content of polychlorinated dibenzofurans (PCDFs) and dibenzo-p-dioxins (PCDDs) in the bleaching filtrate in terms of the nordic toxicity equivalent (N-TEQ) was 33.5, 1.15, 0.56, and 0.014 pg/L for the E, C, H1, and H2 bleaching stages, respectively. The corresponding PCDFs and PCDDs loads in ng/t ADP were in the same ranking, i.e., 670, 69, 11.2, and 0.28, respectively. The congener and isomeric pattern of PCDFs and PCDDs of the bleaching filtrate and the bleached pulp was found to be typical for the chlorine bleaching plant effluent. The obtained dioxin load formed in the mill is in agreement with Western studies for the given multiple chlorine of 0.21-0.23. The load is, however, lower than reported discharges from Scandinavian mills using 1980s bleaching technologies, but substantially higher than the discharges from mills with modern bleaching technologies. Modifications in the bleaching plant to reduce molecular chlorine use are necessary to reduce dioxin formation.http://link.springer-ny.com/link/service/journals/00244/bibs/37n3p303.html

Microsomal prostaglandin E synthase-1 (mPGES-1) is the major enzyme catalyzing the isomerization of prostaglandin (PG) H(2) to PGE(2). Here we report the development of a robust and practical automated assay in a 384-well format for room temperature screening of mPGES-1 inhibitors with high precision and low reagent consumption. The assay should enable precise structure-activity relationship development. It uses acetonitrile as solvent for PGH(2), FeCl(2)/citrate as stop reagent, and a short reaction time. Combined with high-precision liquid transfer and extensive mixing after addition of reactants, these properties let the assay reach Z'>> 0.7 and high reproducibility of inhibitor IC(50) values. Thorough investigation of the quality of mixing in all liquid transfer steps proved crucial for reaching high-precision performance.

BACKGROUND

mPGES-1 (microsomal prostaglandin E synthase-1); FRET (fluorescence resonance energy transfer); HTRF (homogeneous time-resolved fluorescence); PGH2 (prostaglandin H2); PGE2 (prostaglandin E2); SAR (structure-activity relationship); COX-2 (cyclooxygenase-2); GSH (glutathione); ALP (automated labware positioner).

The chain-forming dinoflagellate Gymnodinium catenatum was exposed to hydrogen peroxide. Microscopical examination revealed striking dose-response alterations in chain formation above 245 μm: singlets replaced the dominance of long chain formations. These observations were valid for cells acclimated to halogen light. Under fluorescent light, cells were more resistant to modifications in chain length after H2 O2 exposure. Growth along 9 h in the presence of extracellular H2 O2 followed an hormesis response in both light regimes. Under halogen light conditions, alterations in chain formation and net growth were related to culture time, inocula concentration and geomagnetic activity (GMA) in the proceeding hours. Below a 16 nT threshold in GMA average growth was 0%, while above 16 nT it was circa +9%, independently if the local static magnetic field was altered by a permanent magnet or not. Mycosporine-like amino acids that can have an antioxidant role and are easily oxidized decreased from 7.1 to 6.5 pg cell-1 (P < 0.05) under halogen light and exposure to 245 μm H2 O2 . GMA, as well as UV-A, increased stress responsiveness that can momentarily protect cells from extracellular H2 O2 addition. However, stress response is dependent on bio-availability of several micronutrients and macronutrients, many found at limiting concentrations in oceanic waters.

This research is an investigation of the feasibility of utilizing phosphogypsum (PG) and phosphate tailings (PTS) for cemented paste backfill. Some experiments were conducted with various combinations of PTS and PG as aggregates, along with slags and/or Portland cement as binders and CaO as an additive. The influence of the PG's ageing time on the consolidation of backfill was also explored. The unconfined compressive strength (UCS), the generated gases and the scanning electron microscope (SEM) were all tested and used in the analysis of backfill characteristics. The results show that (i) the highest UCS of backfill prepared by PG and PTS after curing for either 7 days or 28 days is still less than 1.0 MPa, with a large amount of CO2 and SO2 generated; (ii) the slags can improve the UCS by a factor of three, but not without a vast generation of CO2, SO2, and H2S. However, the gases were not produced when CaO was added, but the UCS decreases suddenly to 0.2 or 0.4 MPa after curing for 7 days or 28 days, respectively; (iii) the UCS of backfill increases linearly with increasing cement content. When the CaO was added at 2%, the UCS reached 3.36 MPa after curing for 7 days and 4.44 MPa after curing for 28 days, and no gases were generated; (iv) the influence of the PG's ageing time on the UCS is negligible after 4 days of aging. Based on these results, it was concluded that PG and PTS can be utilized as backfill materials when Portland cement is used as a binder and CaO is used as an additive.

Tachyphylaxis to stimulation of gastric juice secretion during intravenous pentagastrin (PG) infusion has been reported in animal studies. We assessed the course of gastric response to PG 2 micrograms/kg/hr over eight hours in eight healthy subjects. Peak H+, pepsin, and volume secretions occurred during the second half hour of stimulation. Peak H+ output was 11.6 +/- 1.3 mmol/0.5 hr or 7.6 +/- 0.8% of the total eight-hour secretion. During subsequent half-hour collection intervals, there was no significant decline in response, and the average output was 10.3 +/- 0.4 mmol/0.5 hr (6.5 +/- 0.1%). Peak pepsin and volume secretions were respectively 10.0 +/- 1.4% (74.8 +/- 11.6 mg/0.5 hr) and 8.8 +/- 1.1% (146.3 +/- 17.4 mL/0.5 hr) of the total eight-hour secretion. Although there was a significant decline in pepsin and volume response subsequent to the peak output, the decline was not continuous, and pepsin and volume secretions were maintained, respectively, at 6.0 +/- 0.2% (46.1 +/- 2.5 mg/0.5 hr) and 6.2 +/- 0.1% (107.5 +/- 3.0 mL/0.5 hr) of the total eight-hour secretion. Our study did not demonstrate any tachyphylaxis in H+ response to continuous PG stimulation. This model appears to be a valid tool for the assessment of histamine-H2 antagonist effects on stimulated gastric juice secretion over 8 hours in humans.

The mechanisms of arsenic gas phase enrichment (GPE) by dielectric barrier discharge (DBD) was investigated via X-ray photoelectron spectroscopy (XPS), in situ fiber optic spectrometer (FOS), etc. It proved for the first time that the arsenic species during DBD trapping, release, and transportation to the atomic fluorescence spectrometer (AFS) are probably oxides, free atoms, and atom clusters, respectively. Accordingly, a novel in situ DBD trap as a GPE approach was redesigned using three-concentric quartz tube design and a modified gas line system. After trapping by O2 at 9.2 kV, sweeping for 180 s, and releasing by H2 at 9.5 kV, 2.8 pg detection limit (LOD) was achieved without extra preconcentration (sampling volume = 2 mL) as well as 4-fold enhancement in absolute sensitivity and ∼10 s sampling time. The linearity reached R2>> 0.998 in the 0.1-8 μg/L range. The mean spiked recoveries for tap, river, lake, and seawater samples were 100-106%; and the measurements of the certified reference materials (CRMs) were in good agreement with the certified values. In situ DBD trap is also suitable to atomic absorption spectrometry (AAS) or optical emission spectrometry (OES) for fast and on-site determination of multielements.

1. The effects of CGS 22652, a thromboxane (Tx) A2 synthase inhibitor and TxA2/prostaglandin (PG) H2 receptor antagonist, on blood pressure (BP) were studied in conscious freely moving spontaneously hypertensive rats (SHR). 2. Three groups of 13 male SHR were subcutaneously infused from 5 to 11 weeks of age via osmotic minipumps with CGS 22652 at doses of 5 (SHRa) or 10 (SHRb) mg/kg per 24 h or with the vehicle only (SHRc). A fourth group (SHRd, n = 13) was orally treated from 3 to 11 weeks of age with CGS 22652 (30 mg/kg) given by gavage once a day. 3. CGS 22652 dose-dependently reduced the age-related increase in systolic BP. The pressor response to noradrenaline (200 ng/kg, i.v.) but not to angiotensin I or II was slightly (P < 0.05) diminished in 11 week old SHRb and SHRd compared to SHRc. Acute ganglionic blockade by trimethaphan (10 mg/kg, i.v.), as well as angiotensin converting enzyme inhibition by perindopril (2 mg/kg, i.v.) decreased BP to a similar extent in the four groups. After combined blockade of vasopressin receptors and of the autonomic nervous system and the administration of a direct vasodilator (hydralazine, 3 mg/kg, i.v.), the residual mean BP was identical in the four groups of rats. 4. Chronic treatment with CGS 22652 dose-dependent antagonized the TxA2/PGH2 receptors but did not modify the TxA2 synthesis. The urinary sodium excretion did not differ between groups. 5. In conclusion, at the doses used, CGS 22652 given either orally or subcutaneously exhibited only TxA2/PGH2 receptor blocking properties in SHR.(ABSTRACT TRUNCATED AT 250 WORDS)

Prostaglandin (PG) H2 produced a transient contraction followed by a relaxation in helical strips of dog coronary, mesenteric and renal arteries contracted with PGF2 alpha. The contraction was in the order of mesenteric greater than renal greater than coronary artery. Removal of endothelium abolished the contraction in these arteries and significantly potentiated the relaxation only in mesenteric arteries. The relaxation was greater in mesenteric arteries than in renal and coronary arteries, denuded of endothelium. PGI2-induced relaxations were not influenced by endothelium denudation. In the arteries contracted with K+, PGH2-induced relaxations were attenuated, compared to those contracted with PGF2 alpha. Treatment with ONO3708, an antagonist of vasoconstrictor PGs, abolished the PGH2-induced contraction and potentiated the relaxation in the K+-contracted arteries. The relaxant response was suppressed by diphloretin phosphate, a PG receptor antagonist, as was the response to PGI2. PGH2-induced contractions in dog coronary, mesenteric and renal arteries would be due to vasoconstrictor PGs produced preferentially in the endothelium. However, production of PGI2 from PGH2 in endothelial and subendothelial tissues do not appear to differ.

The influence of renal perfusion pressure (RPP) on renal functions was studied in anesthetized 8-wk-old Lyon hypertensive (LH) and normotensive (LN) rats before and after a specific blockade of prostaglandin (PG) H2-thromboxane (Tx) A2 receptors using GR-32191B. The nervous and hormonal influences on the kidneys were controlled by renal denervation, adrenalectomy, and an infusion of norepinephrine, aldosterone, hydrocortisone, and vasopressin. With the use of inflatable cuffs, RPP was varied from 100 to 125 and then to 150 mmHg. In control conditions, the renal blood flow (RBF) and glomerular filtration rate (GFR) were independent of RPP in both strains. LH kidneys differed from LN controls by an increased preglomerular vasoconstriction as indicated by a similar decrease in RBF and GFR. Moreover, the pressure-natriuresis curve was blunted in LH compared with LN kidneys. GR-32191B did not affect the renal function of LN rats. In LH kidneys, it normalized RBF and renal vascular resistance and improved GFR, whereas it had no effect on the pressure-natriuretic relationship. It is concluded that the elevated preglomerular vascular resistance that characterizes LH rats is dependent on an overstimulation of PGH2-TxA2 receptors whereas these latter are not involved in the control of pressure-natriuresis.

7-Oxabicyclo[2.2.1]heptane analogs of prostaglandin (PG) H2 can act as thromboxane (Tx) A2 receptor antagonists or agonists, PGI2 and/or PGD2 receptor agonists, or exhibit a mixture of the above activities. SQ 28,852, a new analog with a hexyloxymethyl omega side chain, is a potent inhibitor of PG synthesis. SQ 28,852 inhibited collagen and arachidonic acid (AA)-induced platelet aggregation and TxB2 and PGE2 formation, but did not block platelet aggregation induced by ADP or the TxA2 mimics, 9,11-azo PGH2, SQ 26,655, and U-46,619. It also blocked conversion of AA to TxB2, PGE2, and 6-keto PGF1 alpha by microsomal preparations of human platelets, bovine seminal vesicles, and bovine aortas, respectively, but did not inhibit the conversion of PGH2 to TxA2 by the platelet microsomal preparation. SQ 28,852 (p.o.) protected mice against the lethal effects of AA (75 mg/kg, i.v.). The I50 values for SQ 28,852, indomethacin and aspirin were 0.025, 0.05 and 15 mg/kg, respectively. Neither SQ 28,852 nor indomethacin protected mice from death caused by 9,11-azo PGH2. SQ 28,852 (0.01 to 1 mg/kg, i.v.) inhibited AA-induced bronchoconstriction in anesthetized guinea pigs for at least 60 min. As an inhibitor of AA-induced bronchoconstriction, SQ 28,852 was 16- and 45-times more potent than indomethacin at 3 and 60 min after i.v. administration, respectively. SQ 28,852 did not inhibit bronchoconstriction induced by histamine or 9,11-azo PGH2, indicating its specificity of action in vivo. SQ 28,852 is the first example of a new class of cyclooxygenase inhibitors whose structure is similar to that of the naturally occurring endoperoxide, PGH2.

The activity of 13,14-dihydroprostaglandin F2 alpha (13,14 H2-PGF2 alpha) synthetase, which catalyzes the conversion of 13,14-dihydro-15-keto-PGF2 alpha (15KD-PGF2 alpha) to 13,14H2-PGF2 alpha, was examined in ovarian cytosol of rat, hamster, mouse, rabbit, guinea-pig, pig, cow and dog. The activity was very low in all species except the rat. The tissue distribution of 13,14H2-PGF2 alpha synthetase in the rat was next studied, and the highest activities were observed in the ovary and adrenal gland, whereas the activities in the lung and kidney, which possess higher activities of 15-hydroxy-PG dehydrogenase, were much lower. The bulk (80%) of the activity in the ovary was recovered in the cytosol fraction. The enzyme from rat ovarian cytosol showed two optimum pH values, at pH 7.0 and pH 8.0. The enzyme activity was strongly inhibited by sulfhydryl reagents and quercitrin, but not by phenobarbital. It is suggested that 13,14H2-PGF2 alpha synthetase in rat ovarian cytosol is a carbonyl reductase, and may be involved in drug metabolism in the female reproductive system.

Recent advances in molecular biological studies on the metabolism and action mechanisms of lipid mediators: arachidonic acid metabolites (eicosanoids) and platelet-activating factor (PAF), are reviewed, in relation to their roles in the kidney. For the last decade, almost all the enzymes involved in three major arachidonic acid metabolic pathways; cyclooxygenase, lipoxygenase and epoxygenase pathways, have been purified and almost all of their cDNA have been cloned. Recently, cDNAs encoding three receptors for lipid mediators; PAF receptor, thromboxane A2/prostaglandin (PG) H2 receptor and a subtype of PGE2 receptor; EP3, were cloned. These advances have facilitated our knowledges of the physiological, pathophysiological roles of these lipid mediators in the kidney.

A photocolorimetric method has been employed for kinetic investigation of aggregation of human platelets under the effects of arachidonic acid (AA) and the products of its metabolism in the platelets. The platelet aggregation was induced by AA and prostaglandin (PG)H2, the precursors of thromboxane (Tx). The initial rate of aggregation depended on AA and PGH2, concentrations. The nature of the influence of selective inhibitors of PGH-synthetase (indomethacin) and PGH-convertase (imidazole) on the rate of aggregation is suggestive of the rate-limiting type of enzymatic reactions of AA conversion into TxA2. Addition to the platelet suspension of solubilized PGH-convertase accelerates the PGH2-induced aggregation. Analysis of platelet aggregation processes induced by AA and PGH2 demonstrated that the enzymatic synthesis of TxA2 is one of the rate-limiting steps within the framework of molecular modifications responsible for the platelet aggregate formation.