ATP increases head volume in capacitated human sperm via a purinergic channel.

Scanning ion-conductance microscopy allowed us to document an external Ca2+ dependent ATP driven volume increase (ATPVI) in capacitated human sperm heads. We examined the involvement of purinergic receptors (PRs) P2X2R and P2X4R in ATPVI using their co-agonists progesterone and Ivermectin (Iver), and Cu2+, which co-activates P2X2Rs and inhibits P2X4Rs. Iver enhanced ATPVI and Cu2+ and 5BDBD inhibited it, indicating P2X4Rs contributed to this response. Moreover, Cu2+ and 5BDBD inhibited the ATP-induced acrosome reaction (AR) which was enhanced by Iver. ATP increased the concentration of intracellular Ca2+ ([Ca2+] i) in >45% of individual sperm, most of which underwent AR monitored using FM4-64. Our findings suggest that human sperm P2X4R activation by ATP increases [Ca2+] i mainly due to Ca2+ influx which leads to a sperm head volume increase, likely involving acrosomal swelling, and resulting in AR. • External ATP induces a volume increase (ATPVI) in capacitated human sperm heads. • Ivermectin enhances ATPVI and Cu2+, and 5BDBD inhibits it, indicating P2X4Rs contributes to this response. • The ATP-induced acrosome reaction showed the same pharmacological profile as ATPVI. • ATP increased intracellular Ca2+ in 45% of sperm, most of which underwent AR. • P2X4R activation causes ATPVI, putative acrosomal swelling, and results in AR. [ABSTRACT FROM AUTHOR]