The effect of zinc on stallion sperm motility

Abstract

Understanding the control of sperm motility in the horse may help to improve the success of equine in vitro fertilization. In humans, zinc (Zn) is found in high concentrations in the seminal plasma, and has been shown to block the sperm proton channel HVCN1. This effect prevents intracellular alkalinization and is thought to help regulate sperm motility. The aim of our study was to measure Zn levels in stallion reproductive fluids and tissues and to evaluate the effect of different concentrations of Zn on equine sperm motility parameters. Zinc levels were measured through flame atomic absorption spectroscopy. Average Zn concentrations (n 1⁄4 5 stallions) in serum, seminal plasma and epididymal fluidwere 8 mM, 24 mMand 87 mM respectively. Within tissues of the internal reproductive tract (n 1⁄4 2 stallions), the highest values for Zn were found in the bulbourethral glands (841 mM) and the lowest in the prostate (261 mM). The various tissue components of the testis contained 214 to 229 mM Zn. In a fractionated ejaculate (n 1⁄4 1 stallion), Zn concentrations were lowest in the pre-sperm fraction (1.8 mM) and highest in the sperm-rich fraction (35 mM). To assess the effect of Zn on sperm motility, ejaculates were collected from 3 fertile stallions, and sperm were washed and incubated in modified Whitten’s media at pH 7.1 to 7.4, with 0, 10, 50, 100 or 500 mM of ZnCl2, at 38 C in humidified air for 30 min. Five motility parameters (total motility (TMOT), progressive motility (PMOT), average-path velocity (VAP), curvilinear