Effect of Phytohemagglutinin on Lymphocyte Membrane Transport

Abstract

Uptake of labelled uridine into lymphocytes is restricted. Several lines of evidence, including experiments with dipyridamole, an inhibitor for membrane transport processes, and kinetic experiments indicate that transport of uridine through the cell membrane is the rate‐limiting step in uridine uptake. Addition of phytohemagglutinin results in an immediate increase of uridine uptake. Saturation experiments have shown that this change is due to an increase in V , whereas the apparent K m value remains constant. The hypothesis is advanced, that phytohemagglutinin induces an increase in the number of functional carrier sites of the membrane transport system.