Direct effects of ethane dimethanesulphonate on epididymal function in adult rats. An in vitro demonstration.

It was recently demonstrated that the Leydig cell toxicant ethane dimethanesulphonate (EDS) produces multiple effects on the epididymis after a single in vivo exposure. To determine whether any of the perturbations were mediated by a direct action of the compound, we used a novel system for the coculture of epididymal epithelial cells and sperm from the caput epididymidis. This system maintains the morphologic integrity and cell polarity of the epididymal epithelial cells before and during coculture, and the sperm recovered after coculture have intact plasma and acrosomal membranes. In addition, several functions required for epididymal sperm maturation are expressed, including the secretion of protein by the epididymal epithelium, the association of secreted protein with the plasma membrane of cocultured sperm, and the acquisition of progressive motility by cocultured sperm. In vitro exposure of epididymal epithelial cells and sperm to EDS results in a significant decline in protein secretion by the epithelial cells during coculture, and in particular, a dose-dependent decline in a 36- to 38-kd protein (PI 4.0 to 4.5) and a 34- to 36-kd protein (PI 4.5 to 5.0). Moreover, these and other proteins are not recovered from the sperm membrane of cocultured sperm after EDS treatment. Finally, EDS results in a dose-dependent decline in the percentage of both motile and progressively motile sperm recovered after coculture compared with that of sperm from untreated cocultures. These effects on sperm motility were not observed when sperm were pretreated with EDS and subsequently cocultured with untreated epithelial cells. We conclude that EDS alters epididymal sperm maturation by acting directly on the epididymal epithelium to mediate changes in sperm membrane protein, and that this may subsequently alter the development of the progressive motility of sperm.