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

Scanning ion-conductance microscopy allowed us to document an external Ca ²⁺ 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 Cu ²⁺ , which co-activates P2X2Rs and inhibits P2X4Rs. Iver enhanced ATPVI and Cu ²⁺ and 5BDBD inhibited it, indicating P2X4Rs contributed to this response. Moreover, Cu ²⁺ and 5BDBD inhibited the ATP-induced acrosome reaction (AR) which was enhanced by Iver. ATP increased the concentration of intracellular Ca ²⁺ ([Ca ²⁺ ] _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 [Ca ²⁺ ] _i mainly due to Ca ²⁺ influx which leads to a sperm head volume increase, likely involving acrosomal swelling, and resulting in AR.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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