Substitution of a synthetic polymer for protein in a mammalian gamete culture system

Polyvinylalcohol (PVA) was tested as a replacement for protein (bovine serum albumin, BSA) in supporting motility, acrosome reactions, and fertilizing ability of hamster spermatozoa in vitro. Bovine serum albumin is normally required for all of these processes. After incubation for 5--6 hours in a simple culture medium containing BSA and PVA (0.1 mg/ml) and essential low molecular weight factors from blood serum, 85% of motile spermatozoa had undergone acrosome reactions. Sperm motility was equally well maintained by PVA in the absence of BSA but virtually no spermatozoa showed acrosome reactions even after prolonged incubation. Serum factors were later replaced by hypotaurine (10 microM), isoproterenol (1 microM), and penicillamine (20 microM). Spermatozoa incubated in this defined medium with BSA alone or with BSA and PVA fertilized more than 90% of oocytes. No oocytes were penetrated when BSA was replaced by PVA although vigorous sperm motility was maintained. Polyvinylalcohol may help elucidate the mechanism of the acrosome reaction by permitting effects of protein and other substances to be studied without loss of sperm motility (viability). Polyvinylalcohol could also replace BSA in solutions used for manipulation of zona pellucida-free oocytes. It is suggested that PVA may find general application in cell culture media.