Breakthroughs in Andrology Chloride Efflux during the Progesterone‐Initiated Human Sperm Acrosome Reaction Is Inhibited by Lavendustin A, a Tyrosine Kinase Inhibitor

Previous studies showed that progesterone (P) can initiate the mammalian sperm acrosome reaction (AR) in vitro and that a sperm GABAA‐like receptor/CI− channel is involved in an essential Cl− efflux mediated by P during the AR. Here, we show that lavendustin A, a potent, specific inhibitor of tyrosine kinase activity, strongly inhibits the P‐initiated human AR and the essential P‐me‐diated Cl− efflux. Lavendustin B, a weak tyrosine kinase inhibitor, had no significant effect. These results suggest that, as part of AR initiation, P mediates tyrosine phosphorylation of the sperm GABAA‐like receptor/Cl− channel.