Effects of Putative Epididymal Osmolytes on Sperm Volume Regulation of Fertile and Infertile c‐ros Transgenic Mice

Abstract

Volume regulation by spermatozoa has been demonstrated to be crucial in both mice and men for transport in the female tract. In order to determine the nature of osmolytes used by spermatozoa, they were released from the cauda epididymis of fertile c-ros heterozygous mice into incubation medium of uterine osmolality (representing an osmotic challenge), containing increasing concentrations of compounds that are major epididymal fluid components and known osmolytes in somatic cells. This should nullify the concentration gradients for osmolytes that mediate volume regulation, prevent osmolyte efflux, and lead to swelling. Of the osmolytes tested, K ϩ caused the most rapid and extensive volume increases; glutamate, taurine, L-carnitine, and myo-inositol also were effective, but glycerophosphocholine was not. Such effects were not observed in cauda sperm from the infertile knockout mice, demonstrating a defect in normal volume regulation. K ϩ concentrations in cauda epididymal fluid were 21 mM higher in the knockout than the heterozygous mice, but no differences were found in caudal fluid glutamate, carnitine, or myo-inositol. The carnitine content of cauda sperm from knockout males was not different from that of fertile males, but lower amounts of glutamate and inositol were found that could explain the poor volume regulation. In heterozygous mice, cauda but not caput sperm responded to the K ϩ channel blocker quinine by swelling, demonstrating development of volume regulation during epididymal transit, whereas knockout cauda sperm showed no response, as with the osmolytes. Major epididymal secretions could serve as osmolytes in murine spermatozoa for volume regulation in response to physiological osmotic challenge in the normal fertile mice; the reduced sperm content of inositol and glutamate in the c-ros knockout mice might reflect maturational abnormalities in volume regulation.Key words: Sperm swelling, regulatory volume decrease, quinine, organic osmolytes, infertility. J Androl 2004;25:216-223A novel cause of male infertility in 2 transgenic mouse models is the angulated tails of spermatozoa that fail to negotiate the uterotubal junction and hence reach the site of fertilization Sipilä et al, 2002). Tail angulation reflects a volume increase in the spermatozoa (Yeung et al, 2002a,b) caused by an inadequate regulatory volume decrease (RVD), which is normally initiated after osmotic entry of water in hypotonic environments. Although somatic cells rarely experience this phenomenon (O'Neill, 1999), it is a normal occurrence for sperm upon ejaculation when they are rapidly expelled into the uterus (osmotic pressure [OP] around 330 mmol/ kg) from the relatively hypertonic environment of the cauda epididymis (OP around 420 mmol/kg) (Yeung et al, 1999). In RVD, the response is to lose cell water in parallel with efflux of osmolytes through pertinent membrane channels. In the early 1970s, studies of bovine ejaculated sperm incubated in medium with osmolality identical to serum showed that Na ϩ and K ϩ close...

The epididymis, cytoplasmic droplets and male fertility

“…45 These observations are consistent with a role for organic osmolytes in regulating volume in mature sperm cells. The fact that high concentrations of these osmolytes prevent sperm RVD in hypotonic media 45 suggests that they do serve that role in the mouse.…”

“…45 These observations are consistent with a role for organic osmolytes in regulating volume in mature sperm cells. The fact that high concentrations of these osmolytes prevent sperm RVD in hypotonic media 45 suggests that they do serve that role in the mouse. In man, the concentration of organic osmolytes in vas deferens fluid is lower than that in rodents (but still at ,5 mmol l 21 , a thousand times higher than that in blood) and K 1 is a major cation.…”

“…The flagellar angulation of post-coital uterine spermatozoa from c-ros KO mice 23 is a clear demonstration of droplet retention, and these spermatozoa are known to be swollen 79 and to contain less osmolytes than those of heterozygous-type fertile males with straight sperm flagella. 45 Cytoplasmic droplets: possible mechanisms of loss The above speculation also addresses the vexing question of how the droplet is lost, as it could be intimately associated with sperm volume regulation. In the bull, seminal vesicle fluid can release droplets from testicular, mature and immature epididymal spermatozoa.…”

Determinants of sperm quality and fertility in domestic species

“…During its life, the spermatozoon experiences considerable changes in its environment, most notably during maturation within the epididymis and at ejaculation. During epididymal transit, an uptake of osmolytes from epididymal secretions takes place, and spermatozoa acquire the ability to regulate cell volume (Yeung et al 2004a). At ejaculation, they transfer from the hypertonic epididymal environment to the isotonic conditions of seminal plasma and the female genital tract fluids, at which time the spermatozoa experience a considerable osmotic gradient (Yeung et al 2004a(Yeung et al , 2004b and references therein).…”

Myoinositol improves sperm parameters and serum reproductive hormones in patients with idiopathic infertility: a prospective double-blind randomized placebo-controlled study

“…Interestingly, MI is involved in the regulation of intracellular Ca 2+ concentration (Foskett, 2010) and previous evidence suggests a possible role of MI in spermatogenesis and sperm function. Indeed, in transgenic mice, low MI concentration within epididymis has been associated with reduced fertility (Yeung et al, 2004). Moreover, MI increased the number of spermatozoa with high mitochondrial membrane potential (MMP) while it decreased the number of those with low MMP in patients with OAT in vitro (Ching-Hei 2004;Foskett, 2010;Condorelli et al, 2011;Condorelli et al, 2012).…”