The systems that transport ions and their impact on sperm function and male fertility

Sperm are highly specialized cells whose primary function is to transport and deliver the paternal genetic information to the oocyte. Although morphologically complete after being produced in the testis, sperm acquire fertilizing competence through a series of post-testicular maturation steps. During this journey, cues from the surrounding luminal fluids play a crucial role in sperm functional maturation. Among these signals, changes in the ion composition of the extracellular medium are particularly important. Sperm detect these ion fluctuations and regulate their intracellular ion concentrations through membrane ion transport systems. While some of these transporters are shared with somatic cells, others have evolved as specialized molecular variants uniquely adapted to meet the specific physiological demands of sperm. Genetic mutations and dysfunction of certain ion transporters have been associated to male infertility. Consequently, ion transporters represent promising diagnostic markers for the detection of male infertility and are attractive pharmacological targets for the development of therapies to enhance or inhibit male fertility. This review provides a comprehensive analysis of the ion transport systems that operate in sperm membranes and discusses their function, regulation, and contribution to the overall physiology of sperm.