UPTAKE OF 5‐HYDROXYTRYPTAMINE BY PLATELETS

Abstract

Human blood platelets were incubated with 5‐hydroxytryptamine and with tryptamine and the uptake of each amine measured. The uptake of tryptamine, unlike that of 5‐hydroxytryptamine, was linearly related to the concentration of the amine in the surrounding fluid, was similar in amount at 0° and 37° C and varied directly with the pH of the solution. When both amines were present together the uptake of 5‐hydroxytryptamine was depressed. The antagonism of tryptamine was found to be competitive, and the possible site of its action is discussed. The effect of a number of other substances on the uptake of 5‐hydroxytryptamine by platelets was examined; of these imipramine, cocaine and chlorpromazine were more potent and dihydroergotamine and lysergic acid diethylamide somewhat less potent than tryptamine in inhibiting uptake. 1961 British Pharmacological Society