title: Platelet aggregation and endogenous 5-HT secretion in presence of Ca2+, Sr2+ and Ba2+. Effects of calcium antagonists.
abstract: Washed rat platelets aggregation and endogenous serotonin release were studied after thrombin stimulation in the presence of different concentrations of Ca2+, Sr2+ or Ba2+. The extent of platelet aggregation and release was found to depend upon the external concentration of these cations. For all of them, an optimum concentration could be defined. Higher concentrations were shown to inhibit both aggregation and release. Efficiency to support thrombin-induced aggregation was in the order Ca2+ greater than Sr2+ greater than Ba2+. Complete inhibition of aggregation and release induced by thrombin was obtained after a 30 second preincubation with 38 uM nitrendipine, 1 mM Cd2+ or 1 mM Mn2+. Inhibition was obtained in the presence of Ca2+, Sr2+ or Ba2+. These results are consistent with the hypothesis that Sr2+ and Ba2+ are able to support platelet activation acting as Ca2+ substitutes. Following thrombin stimulation, they could penetrate the platelets and mimick a rise in cytoplasmic Ca2+.
mesh_terms: D000818:Animals; D001464:Barium / Q000502:physiology*; D001792:Blood Platelets / Q000502:physiology; D002118:Calcium / Q000037:antagonists & inhibitors / Q000502:physiology*; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D008297:Male; D009568:Nitrendipine / Q000494:pharmacology; D010974:Platelet Aggregation / Q000187:drug effects*; D051381:Rats; D012701:Serotonin / Q000378:metabolism*; D013324:Strontium / Q000502:physiology*; D013917:Thrombin / Q000494:pharmacology
chemical_list: D002121:Calcium Channel Blockers; D001464:Barium; D012701:Serotonin; D009568:Nitrendipine; D013917:Thrombin; D002118:Calcium; D013324:Strontium