EFFECT OF COLD TREATMENT AND SOME DRUGS ON THE 5-HYDROXYTRYPTAMINE UPTAKE BY RABBIT BLOOD PLATELETS AND THEIR ULTRASTRUCTURE

摘要

References(19) Cited-By(2) When utilizing a cold treatment we found that uptake activity of 5-hydroxytryptamine (5HT) by blood platelets of the rabbit was decreased in a non-competitive manner, while endogenous 5HT concentration of the platelets and the platelet counts were not affected. Morphologically, the cold treatment induced a dissociation and disappearance of circumferential bands of microtubules (CB-Mt) and the platelets, protruding pseudopods, lost their discoidal shape. Incubation of platelets with colchicine or vinblastine provided similar morphological alterations of CB-Mt, but there was only a slight inhibition toward the 5HT uptake, a finding which indicated that CB-Mt of platelets do not play an essential role in the 5HT uptake system of platelets. The decreased 5HT uptake by the cold treatment was sharply restored by addition of theophylline to the medium, but not by dibutyryl cyclic AMP. The former also significantly enhanced the 5HT uptake by the intact platelets, and this effect was potentiated by prostaglandin E1 (PG-E1), but not by prostaglandin E2 (PG-E2). The possibility is raised that only endogenous cyclic AMP may regulate the 5HT uptake system of platelets. Pluronic F68, non-ionic detergent, had no effect on 5HT uptake by the intact platelets but stimulated the effect of the cold treatment, probably through facilitating conformational change of membrane induced by the treatment.