Progesterone stimulates GABA uptake in human spermatozoa

Progesterone can initiate the mammalian sperm acrosome reaction in vitro, and studies on the effect of progesterone and several other steroids have demonstrated an increased calcium influx following binding to the sperm membrane. We have previously presented data indicating the presence of a GABA transport protein in human spermatozoa. In this study, we have examined the uptake of radiolabelled GABA into human spermatozoa in the presence of progesterone, other steroids known to elevate intracellular calcium, and steroids known to be ineffective as stimulators of calcium influx. The results demonstrate a twofold increase in GABA uptake following preincubation with progesterone or steroids known to stimulate calcium influx. Steroids with minor effects on calcium influx were less effective as stimulators of GABA uptake. (C) 1996 Academic Press, Inc.