VARIATION OF MOUSE OOCYTE SENSITIVITY TO GRISEOFULVIN-INDUCED ANEUPLOIDY AND MEIOTIC DELAY DURING THE FIRST MEIOTIC DIVISION

The effects of varying the time of chemical treatment on the induction of aneuploidy and meiotic delay in metaphase II (MII) oocytes were st udied by administering 1,500 mg/kg griseofulvin (GF) at 0, 2, 4, 6, or 8 hr after an injection of human chorionic gonadotrophin (HCG). The r esults show that the oocytes have a different sensitivity to GF-induce d aneuploidy and meiotic delay during the course of meiotic maturation . Although not restricted to a particular period of meiotic maturation , the frequency of aneuploidy was highest (P < 0.05) when GF was given at 2, 4, or 6 hr after HCG. The maximum frequency of hyperploidy (42. 4%) occurred at the 4-hr treatment time. Also, GF treatment resulted i n the induction of meiotic delay as demonstrated by ovulated metaphase I (MI) and polyploid MII oocytes. The meiotic delay data depict a per iod of relative resistance between two periods of sensitivity in that the percentages of ovulated MI oocytes were 53.3, 21.3, 3.5, 6.7, and 25.7 when GF was given at 0, 2, 4, 6, and 8 hr after HCG, respectively . Also, at these treatment times the percentages of polyploid oocytes were 0.6, 1.7, 7.7, 20.1, and 15.4, respectively. Therefore, the oocyt es seem to be more sensitive to GF-induced meiotic delay during the pe riods preceding and following meiotic spindle assembly. In conclusion, the results demonstrate that the time of chemical treatment influence s the frequency of aneuploidy and the degree of meiotic delay. Also, t he results emphasize that to thoroughly characterize the aneugenic pot ential of a specific chemical several treatment times may be needed. ( C) 1994 Woley-Liss, Inc.