DOSE-RESPONSE STUDY AND THRESHOLD ESTIMATION OF GRISEOFULVIN-INDUCED ANEUPLOIDY DURING FEMALE MOUSE MEIOSIS-I AND MEIOSIS-II

The relative sensitivity of the two meiotic divisions of mouse oogenes is to griseofulvin (GF)-induced aneuploidy was investigated. The first meiotic division was studied by administering GF 4 h after human chor ionic gonadotrophin (HCG) injection and analyzing metaphase II (MII) o ocytes, whereas study of the second meiotic division involved treating the females 10 h after HCG and analyzing one-cell (1-Cl) zygotes, Dat a from previous studies have shown that these treatment times represen ted the most sensitive times for aneuploidy induction during meioses I and II. The statistical analyses of the data showed that the dose-res ponse curves for aneuploidy induction did not differ quantitatively or qualitatively between the two meiotic divisions. The percentages of h yperploid MTI oocytes and 1-Cl zygotes were significantly higher (P < 0.001) than in the controls for all doses except 125 mg/kg GF. The hig hest percentages of hyperploid cells were found after administering 15 00 mg/kg GF, However, these percentages were not different (P > 0.05) from those observed after 500 or 1000 mg/kg GF, suggesting saturation of the GF aneuploid target(s), These results suggest that the relative sensitivity to GF-induced aneuploidy between the two meiotic division s of oogenesis are similar. They also suggest the presence of a lower (125 mg/kg) and an upper (500 mg/kg) threshold for GF-induced aneuploi dy.