Regulation of the motility and metabolism of spermatozoa for storage in the epididymis of eutherian and marsupial mammals
Department of Biological Sciences, University of Newcastle, NSW, Australia.Reproduction Fertility and Development (Impact Factor: 2.4). 02/1996; 8(4):553-68. DOI: 10.1071/RD9960553
The present review examines the mechanisms involved in sperm storage in the epididymis of therian mammals in terms of the supply of energy substrate and the regulation of motility and metabolism. Lipids, glucose, lactate and glycerol are possible metabolic substrates for sperm in the epididymis, but the role of these is uncertain and it may differ between marsupials and eutherians. Sperm are normally immotile in the epididymis, but ram and rabbit sperm may have an uncoordinated motility. Sperm metabolism is suppressed but is probably not strongly coupled to motility. Work on diluted sperm indicates that cyclic adenosine monophosphate, Ca2+, and pH play roles as intracellular messengers controlling the motility and metabolism of sperm, but no first messenger has been identified. A number of mechanisms of suppressing sperm motility and metabolism in the epididymis are considered, including a collective autoregulation, oxygen tension, osmotic pressure, viscosity and the extracellular concentration of H+, Ca2+, Na+, HCO3- and carnitine. However, there is no conclusive evidence for any of the mechanisms and there is clearly some variation between species in the mechanism of suppressing sperm activity. Sperm activation stimulates motility and a 4-5-fold increase in respiration rate that has not been reversed without compromising viability. Following activation, respiration supported by endogenous and/or exogenous substrates is much higher in marsupial than eutherian sperm, and marsupial sperm do not show a large stimulation of respiration on the addition of exogenous substrate, as is characteristic of most eutherian sperm.
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- "Although a complex array of proteins and secretory products in the epididymis have been identified , a detailed understanding of how they influence the cellular changes that occur to spermatozoa at different sites of the epididymis is still largely unknown. The caudal epididymis and caudal fluid in particular provide an important environment that supports sperm survival during storage and the acquisition of fertilizing capacity  . Numerous studies have shown the unique composition of caudal fluid when compared to secretions in proximal segments of the epididymis. "
ABSTRACT: The sperm reservoir is formed when spermatozoa bind to the epithelium of the utero-tubal junction and caudal isthmus of the oviduct. It is an important mechanism that helps synchronize the meeting of gametes by regulating untimely capacitation and polyspermic fertilisation. This study investigated the influence of epididymal maturation and caudal fluid on the ability of spermatozoa to bind to oviduct epithelium using a model porcine oviduct explant assay. Spermatozoa from the rete testis, middle caput (E2-E3), middle corpus (E6) and cauda (E8) of Large White or Large White x Landrace boars at 10-14 months of age were diluted in modified Androhep solution and incubated with porcine oviduct explants. Results reported in this study support our hypothesis that testicular spermatozoa need to pass through the regions of the epididymis in order to acquire the ability to bind to the oviduct. There was a sequential increase in the number of spermatozoa that bound to oviduct explants from the rete testis to caudal epididymis. Binding of caudal spermatozoa to isthmic explants was the highest (15.0 ± 1.2 spermatozoa per 1.25 mm2; mean ± standard error of the mean; P ≤ 0.05) and lowest by spermatozoa from the rete testis (2.0 ± 0.3 per 1.25 mm2), and higher to isthmus from sows compared to gilts (35.8 ± 6.7 per 1.25 mm2vs. 14.8 ± 3.0 per 1.25 mm2; P ≤ 0.05). Binding of ejaculated spermatozoa to porcine isthmus was higher than for caudal spermatozoa (26.3 ± 1.4 per 1.25 mm2vs. 15.0 ± 0.8 per 1.25 mm2; P ≤ 0.05), and higher to porcine than to bovine isthmus (26.3 ± 2.3 per 1.25 mm2vs. 18.8 ± 1.9 per 1.25 mm2; P ≤ 0.05). Incubation of spermatozoa from the caput and corpus in caudal fluid increased the ability of spermatozoa to bind to oviduct epithelium (P ≤ 0.05). In conclusion, the capacity of testicular spermatozoa to bind to oviduct epithelium increases during their maturation in the epididymis, and can be advanced by components of the caudal fluid.
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- "It has been known for more than sixty years that the luminal fluid of the female reproductive tract has a HCO 3 À content two to four times higher than that of the plasma (Vishwakarma, 1962; Murdoch and White, 1968; Maas et al., 1977). It is also known that HCO 3 À is essential to a number of reproductive events occurring in the female reproductive tract (Chan et al., 2006, 2009, 2012; Liu et al., 2012), including sperm motility (Mann and Lutwak-Mann, 1982; Tajima et al., 1987; Jones and Murdoch, 1996; Abaigar et al., 1999; Holt and Harrison, 2002; Wennemuth et al., 2003; Wennemuth, 2004; Mannowetz et al., 2011), capacitation (Boatman and Robbins, 1991; Shi and Roldan, 1995; Zhou et al., 2005), a sperm activation process by which sperm acquire their ability to fertilise the egg, and early embryo development (Chen et al., 2010; Lu et al., 2012). The questions as to how HCO 3 À is secreted into the lumen of the female reproductive tract and how HCO 3 À is transported into sperm and embryo have not been fully addressed. "
ABSTRACT: The solute carrier 26 (SLC26) family emerges as a distinct class of anion transporters with its members SLC26A3 (Slc26a3) and SLC26A6 (Slc26a6) reported to be electrogenic Cl(-) /HCO3 (-) exchangers. While it is known that uterine fluid has high HCO3 (-) content and that HCO3 (-) is essential for sperm capacitation, the molecular mechanisms underlying the transport of HCO3 (-) across uterine epithelial cells and sperm have not been fully investigated. The present review re-examines the results from early reports studying anion transport, finding clues for the involvement of Cl(-) /HCO3 (-) anion exchanges in electrogenic HCO3 (-) transport across endometrial epithelium. We also summarize recent work on Slc26a3 and Slc26a6 in uterine epithelial cells and sperm, revealing their functional role in working closely with the cystic fibrosis transmembrane conductance regulator (CFTR) for HCO3 (-) transport in these cells. The possible involvement of these anion exchangers in other HCO3 (-) dependent reproductive processes and their implications for infertility are also discussed.
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- "Although it is well established that mammalian sperm must undergo maturation in the epididymis to gain the potential to fertilize an ovum (Bedford 1967, Orgebin-Crist 1967, Sonnenberg-Riethmacher et al. 1996), and then spend time in the female tract in order to capacitate before they can actually fertilize an ovum (Austin 1951, Chang 1951), the need for extra-testicular sperm maturation in birds is contentious. In mammals, sperm maturation involves structural modifications, changes in the lipid and protein composition of the plasmalemma (Jones 1989, 1998), and development of a characteristic pattern of motility (Morton et al. 1978, Jones & Murdoch 1996). "
ABSTRACT: The role of the avian epididymis in post-testicular development and capacitation was examined in order to assess whether avian spermatozoa undergo any processes similar to those characteristic of mammalian sperm development. We found no evidence of a need for quail sperm to undergo capacitation and 90% of testicular sperm could bind to a perivitelline membrane and acrosome react. However, CASA analysis showed that only 20% of testicular sperm from the quail were capable of movement and only about 12% of the motile sperm would have a curvilinear velocity greater than the mean for sperm from the distal epididymis. Nevertheless, epididymal transit was associated with mean increases in sperm velocity and the proportion of motile sperm. Together these findings explain why earlier workers have achieved some fertilizations following inseminations of testicular spermatozoa, but also demonstrate the need for some epididymal maturation of avian spermatozoa. Analysis of the electrophoretic profile of quail epididymal luminal proteins revealed that only one major protein (~16 kDa) is secreted by the epididymis and it was virtually the only protein secreted by the ipsilateral epididymis following unilateral orchidectomy. Mass spectrometry showed that this protein is hemoglobin; this finding was confirmed using anti-hemoglobin antibodies. It is suggested that hemoglobin may support sperm metabolism in the quail epididymis, aid in motility, and/or serve as an antioxidant.