[Sterologic evaluation on in vitro thrombin-induced platelet degranulation and contraction (author's transl)]

Stereologic study of the in vitro release reaction from unstirred washed platelets provided quantitative information on the contractile wave induced by thrombin. Contraction was estimated from the reduction in the volume of both the granular compartment and the vacuoles of the surface connected canalicular system. Dibutyryl cyclic-AMP (10(-4) M) and dipyridamole (10(-3) M) inhibited degranulation, but they had no effect on the contraction produced by thrombin at high concentrations (0.1 UI/ml). Aspirin (10(-4) M) inhibited contraction induced by thrombin at concentration of 0.1 and 0.02 UI/ml (p less than 0.01 at each concentration). In two patients with hereditary cyclo-oxygenase deficiency, contraction produced by thrombin at low concentration (0.02 UI/ml) failed to induce contraction.