CONTRIBUTION OF EPIDIDYMAL FACTORS TO SPERM MATURATION AND STORAGE

In fertile men, the majority of epididymal spermatozoa acquire the pot ential to fertilize (assessed with sperm function assays) on passage i nto the corpus and cauda regions of the epididymis. Although secretion s of the epididymal epithelium are clearly important for sperm maturat ion and survival, their role in this process has yet to be fully deter mined. Alterations in epididymal sperm membranes may result from the i ncorporation of protein, sugar and lipid determinants. Most probably, factors of epididymal origin act in concert with constitutional change s to spermatozoa, which together permit full sperm function. Epididyma l spermatozoa incubated with epididymal epithelial cell cultures can u ndergo some maturation in vitro, which can lead to the development of sperm fertilizing capacity. Go-incubations of human sperm with epididy mal epithelial cultures, at 37 degrees C with medium replenished every other day, led to 50% of spermatozoa retain-ng motility after 8 days. In one case, a few spermatozoa survived for 17 days, the inherent max imal survival time of human spermatozoa in situ. An important aspect o f coculture experiments is that close interactions between spermatozoa and epithelial cells can be examined in detail. This coculture techni que may yield important information related to epididymal sperm matura tion and storage.