Binding and Transport of Serotonin in Rabbit Blood Platelets and Action of Reserpine

Abstract

Evidence for the occurrence of bound serotonin was not demonstrated by various physicochemical procedures using rabbit blood platelets. Thus, when serotonin was separated completely from the platelet proteins, the ultrafiltrate of a platelet homogenate contained the same concentration of serotonin as the unfiltered homogenate and, at equilibrium after dialysis of the platelet homogenate, the concentration of serotonin outside the bag was practically equal to that on the inside. The absorption of serotonin by platelets was stimulated by glucose and this stimulation was inhibited by inhibitors of glucose oxidation and by an uncoupler of oxidative phosphorylation. ATP seemed to be the principal substance stimulating absorption. Reserpine inhibited the absorption stimulated by glucose or ATP. The mechanism of the transport and release are discussed and it is suggested that enzymatic processes may participate in both reactions.