OBJECTIVE

To investigate whether platelets are activated in asthmatics with increased release of preformed mediators and to investigate the influence of oral administration of theophylline on them.

METHODS

Comparison of the intracellular free calcium concentration ([Ca2+]i) in platelets as an indicator of platelet activation, CD62P expression on platelets, and the chemokine regulated upon activation in normal T cells expressed and presumably secreted (RANTES) level in platelet-rich buffer supernatants between asthmatics and normal subjects.

METHODS

The respiratory outpatient clinics, Hiroshima University, Japan.

METHODS

Twenty-five normal volunteers, 19 asthmatics taking no oral drugs associated with asthma treatment (group A), and 18 asthmatics taking oral theophylline (group B).

RESULTS

While the resting [Ca2+]is in platelets were similar among the three groups, the [Ca2+]is in group A were significantly higher than those in normal subjects (p<0.05) and group B (p<0.01) after thrombin or 9,11-epithia-11,12-methano-thromboxane A2 (STA2) stimulation in the absence of external Ca2+. The CD62P expression level and RANTES level in group A after STA2 stimulation were significantly higher than those in normal subjects and group B (p<0.05).

CONCLUSIONS

We conclude that agonist-mediated activation of platelets is augmented in asthmatics resulting in enhanced release of chemokine such as RANTES, which could be suppressed by oral administration of theophylline.