Abstract
Oviductal apical plasma membrane fractions have been successfully used to provide an in vitro model to study the role of direct membrane contact in sperm-oviduct interactions. Apical plasma membrane preparations from pig oviductal tissues show a dose-response in their ability to maintain boar sperm viability in vitro. Membrane preparations obtained from other tissues (lung and duodenum) are incapable of maintaining boar sperm viability to the same extent as oviductal tissue. The present study examined the validity of two hypotheses that arise from current knowledge of sperm-oviduct interactions, namely, that (i) apical plasma membranes prepared from ampullar regions of the oviduct are less effective than those from isthmus regions, and (ii) sperm survival is more effective in apical plasma membrane preparations derived from follicular phase oviducts than those derived from luteal phase oviducts. Both hypotheses were proved false. The nature of the active component(s) in the oviductal apical plasma membrane fractions was further investigated. Heat treatment (100 degrees C for 20 min) diminished the capacity of membranes to support boar sperm viability. Furthermore, a soluble salt-extracted fraction obtained from oviductal apical plasma membrane preparations was biologically active and supported boar sperm viability in vitro. This may indicate that the active factor(s) responsible for the maintenance of boar sperm viability is not an integral part of oviductal membranes and is peripherally bound to these membranes.
Highlights
After mating, inseminated mammalian spermatozoa are transported to the oviduct where a reservoir of spermatozoa is formed
Studies in several species have shown that the reservoir is limited to the caudal isthmus (Hunter, 1981, 1984; Hunter and Nichol, 1983; Smith and Yanagimachi, 1990), where spermatozoa are held until ovulation, when a small number is released to meet the egg(s) (Hunter, 1984; Suarez, 1987; Smith and Yanagimachi, 1991)
Despite the importance of direct membrane contact between oviduct epithelia and spermatozoa, and the possible involvement of oviductal membrane proteins in this interaction, many studies in the past have only investigated the role of oviductal secretory products on spermatozoa
Summary
After mating, inseminated mammalian spermatozoa are transported to the oviduct where a reservoir of spermatozoa is formed. Sperm attachment to oviductal epithelial cells is initiated by uncapacitated spermatozoa (Fazeli et al, 1999) and it appears that carbohydrates are involved in mediating the Despite the importance of direct membrane contact between oviduct epithelia and spermatozoa, and the possible involvement of oviductal membrane proteins in this interaction, many studies in the past have only investigated the role of oviductal secretory products (proteins) on spermatozoa This is partially related to the ease of obtaining oviduct secretory products from in vivo (McNutt et al, 1994; Lapointe and Sirard, 1996; Kawakami et al, 1998, 2000; Rodriguez and Killian, 1998) and in vitro sources (Ijaz et al, 1994; Abe et al, 1995a,b; Lapointe and Sirard, 1998; Martus et al, 1998). In most experimental models (epithelial monolayers or explants), spermatozoa were in contact with the oviductal cells and simultaneously exposed to oviductal c 2003 Society for Reproduction and Fertility 1470-1626/2003
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