Molecular mechanisms of mammalian sperm capacitation, and its regulation by sodium-dependent secondary active transporters.

Background: Mammalian spermatozoa have to be "capacitated" to be fertilization-competent. Capacitation is a collective term for the physiological and biochemical changes in spermatozoa that occur within the female body. However, the regulatory mechanisms underlying capacitation have not been fully elucidated.

Hamster spermatozoa incorporate hypotaurine via TauT for self-protection.

In Brief: Mammalian spermatozoa actively generate reactive oxygen species (ROS) during capacitation, a maturational process necessary for fertilization in vivo. This study shows that hypotaurine, a precursor of taurine present in the oviduct, is incorporated and concentrated in hamster sperm cells via the taurine transporter, TauT, for cytoprotection against self-produced ROS.

Abstract: To achieve fertilization competence, mammalian spermatozoa undergo capacitation, during which they actively generate reactive oxygen species (ROS).

Hamster Sperm Possess Functional Na/Ca-Exchanger 1: Its Implication in Hyperactivation.

Previous studies demonstrated that hamster sperm hyperactivation is suppressed by extracellular Na by lowering intracellular Ca levels, and Na/Ca-exchanger (NCX) specific inhibitors canceled the suppressive effects of extracellular Na. These results suggest the involvement of NCX in the regulation of hyperactivation. However, direct evidence of the presence and functionality of NCX in hamster spermatozoa is still lacking.

Activation of cAMP-dependent phosphorylation pathways is independent of ROS production during mouse sperm capacitation.

Mammalian sperm have to undergo capacitation to fertilize the egg. At the molecular level, capacitation involves cAMP synthesis, protein kinase A activation, and downstream increase in tyrosine phosphorylation. In addition, during capacitation, mammalian sperm actively generate reactive oxygen species (ROS).

Oviductal high concentration of K suppresses hyperpolarization but does not prevent hyperactivation, acrosome reaction and fertilization in hamsters.

Mammalian sperm have to undergo capacitation to be fertilization competent. Capacitated sperm in vitro show hyperpolarization of the membrane potential. It has been reported that in mouse membrane hyperpolarization is necessary for the acrosome reaction.