Changes in guinea pig sperm intracellular sodium and potassium content during capacitation and treatment with monovalent ionophores

Abstract

Guinea pig spermatozoa were collected from the caudae epididymides in various isotonic solutions and the intracellular sodium and potassium content was determined by atomic absorption spectroscopy. The sperm intracellular Na and K content was found to be influenced by large variations in the extracellular concentrations of these ions. Treatment of spermatozoa suspended in a saline‐based solution with the monovalent ionophores monensin or nigericin caused an approximate 2‐fold increase in the intracellular Na content and a 3–6 fold decrease in the intracellular K content. Incubation of the spermatozoa in a K+‐free minimal culture medium (MCM‐PL) at a pH of 7.6 or 8.3 for 2 hr caused an approximate 2‐fold increase in the sperm intracellular Na content and a 5‐fold decrease in the intracellular K content. The motile spermatozoa incubated for 2 hr at pH 7.6 showed less than 5% acrosome reactions, compared with 30–40% acrosome reactions after incubation at pH 8.3, in response to the addition of 5 mM Ca2+. Changes in the sperm intracellular elemental composition during culture in vitro, which may lead to an acrosome reaction, are discussed.

Modulation of spermatozoon acrosome reaction

“…One of these events is spermatozoon capacitation, which encompasses a number of modifi cations that take place as sperm travel along the female reproductive tract and that involve a number of structural and biochemical changes in the spermatozoon (Barros, 1974;Go and Wolf, 1985;Hyne et al, 1985;Llanos, 1989;Fraser, 1995). These changes include an increase in plasma membrane fl uidity, a decrease in the level of plasma cholesterol content (Go and Wolf, 1985;Cross, 1998), an increase in intracellular concentrations of calcium and cAMP (Yanagimachi and Usui, 1974; Yanagimachi, 1982; Visconti Visconti et al, 1995;Visconti and Kopf, 1998), phosphorylation of tyrosine residues in proteins (Visconti et al, 1995;Leclerc et al, 1996), and a shift in the patterns of spermatozoon movement and motility (Yanagimachi, 1970).…”

Activation of GABAAReceptor/Cl−Channel and Capacitation in Rat Spermatozoa: HCO3−and Cl−are Essential

“…It has been shown that Na þ , K þ , Ca þ , HCO 3 À , BSA and energy substrates are important for hyperactivated sperm motility [Burkman et al 1984;Fraser 1983;Hyne et al 1985;Suarez 1996;Yanagimachi 1994]. The reason for the apparent conflict may reflect, at least in part, the use of different sperm capacitating media and the fact that different studies measured hyperactivation by different techniques which measure different stages of capacitation.…”

Cellular Mechanisms During Mammalian Fertilization

“…Na + rises progressively toward serum levels, whereas K+ declines from -90 mM concentrations in seminal secretion to -20-30 mM through the uterus and oviduct (81, 82). These ions may control portions of the capacitation process, as suggested by ion depletion and ionophore studies (226,227,299,303,433). In addition, the external pH influences capacitation, as assayed by fertility and by spontaneous exocytosis.…”