Abstract

Calcium signaling is a fundamental process regulating critical sperm functions, including motility, capacitation, and the acrosome reaction. While the core machinery, notably the sperm-specific CatSper channel, is conserved across mammals, species-specific variations in regulatory mechanisms are hypothesized to account for differences in reproductive physiology. This study presents a comparative investigation into the molecular mechanisms governing the calcium response in human and murine spermatozoa. Using fluorescence ratiometric imaging with Fura-2, we analyzed the kinetics and amplitude of intracellular Ca²⁺ transients in response to key physiological stimuli, including progesterone and alkalization. Our results indicate that while both species exhibit a dependence on CatSper-mediated Ca²⁺ influx, the pharmacological profile of regulatory pathways, particularly those involving P2X receptors and store-operated calcium entry (SOCE), shows significant divergence. Specifically, human sperm demonstrated a heightened sensitivity to P2X receptor agonists, suggesting a more complex, multi-channel regulatory network. These findings highlight critical species-specific differences in sperm Ca²⁺ homeostasis, which are essential for understanding fertilization success and for the development of targeted male contraceptive strategies.