Neutral amino acid transport during the cell cycle of cultured human lymphocytes.

Neutral amino acid (isoleucine, leucine, and valine) transport was monitored in synchronous populations of WIL-2 cells, a diploid human lymphoblastoid B cell line. Cells were synchronized by either the double thymidine block technique or by density-dependent arrest in G1. Cells synchronized by these methods showed up to a 66% decrease in amino acid transport upon progressing from the early S phase through the G2 and M phases with a concomitant increase in transport during the G1 phase. The lowest activities of amino acid transport in synchronized cells were observed during the G2 and M phases.