Abstract
The enzymically catalysed incorporation of N-acetylneuraminic acid into human platelets, whether suspended in their own citrated plasma or in buffered saline containing 0.17 mM-sucrose, accelerated the uptake of 5-hydroxytryptamine. This acceleration decreased with time. The observations may be explained by assuming that N-acetylneuraminic acid is a component of a transport receptor for 5-hydroxytryptamine.