Effect of bovine seminal ribonuclease and bovine pancreatic ribonuclease aon bovine oocyte maturation

Bovine seminal ribonuclease (BS-RNase) contains the MxM (noncovalent dimer) and M=M (free monomer) in constant ratio. The aim of this work was to eval uate the effect of BS-RNase, its monomer and dimer forms, and also various mutants of this enzyme on meiotic completion in cattle oocytes. It was foun d that BS-RNase has irreversible effects on the meiotic maturation of bovin e oocytes in vitro, particularly on the completion of meiosis. The effect o f BS-RNase is dose-dependent. In medium supplemented with 1 mu g/ml, the re sults were comparable with those of the control (70% MII oocytes after 24 h r of culture). Whereas 5 mu g/ml reduced the number of MII oocytes to 50%, 10 and 25 mu g/ml arrested this process completely. The MxM form and RNase A at 5 mu g/ml inhibited the maturation rate by 71 and 48%, respectively, b ut a less significant effect was observed for the M=M form, or the carboxym ethylated monomers MCM31 and MCM32 (21%, 16%, and 42% MII oocytes, respecti vely, in comparison with control). These data demonstrate that bovine ribon ucleases can have variable detrimental effects on the maturation of bovine oocyte. J. Exp. Zool. 287:394-399, 2000. (C) 2000 Wiley-Liss, Inc.