PREOVULATORY DYNAMICS OF OVARIAN-STEROID HORMONES IN 2 MOUSE STRAINS DIFFERING IN THE RATE OF MEIOTIC MATURATION

Immature females of two inbred strains, KE and CBA, differing in the r ate of meiotic maturation, were used in this study. On the 26th day th ey were treated with 5 IU PMSG (0 h) and 48 h later with 5 IU hCG. Gro ups of females were killed at 2 h intervals starting with 46 h and ova ries were then dissected for steroid analysis by appropriate RIAs. In both strains hCG injection resulted in a sharp increase in ovarian pro gesterone content with a simultaneous fall in androgen and oestradiol concentrations. However, in the CBA strain, progesterone concentration starred to rise earlier while androgen concentration decreased later than in the KE strain. This subtle difference could be one of the fact ors contributing to the different maturation rate of KE and CBA strain s.