Starvation induces an increase in intracellular calcium and potentiates the progesterone-induced mouse sperm acrosome reaction

Abstract

We have recently reported two different methodologies that improve sperm functionality. The first method involved transient exposure to the Ca²⁺ ionophore A₂₃₁₈₇ , and the second required sperm incubation in the absence of energy nutrients (starvation). Both methods were associated with an initial loss of motility followed by a rescue step involving ionophore removal or addition of energy metabolites, respectively. In this work, we show that starvation is accompanied by an increase in intracellular Ca²⁺ ([Ca²⁺ ]_i ). Additionally, the starved cells acquire a significantly enhanced capacity to undergo a progesterone-induced acrosome reaction. Electrophysiological measurements show that CatSper channel remains active in starvation conditions. However, the increase in [Ca²⁺ ]_i was also observed in sperm from CatSper null mice. Upon starvation, addition of energy nutrients reversed the effects on [Ca²⁺ ]_i and decreased the effect of progesterone on the acrosome reaction to control levels. These data indicate that both methods have common molecular features.

Keywords: CatSper; acrosome reaction; intracellular calcium; mice sperm; progesterone; starving.