Methylmercury effects on Syrian hamster metaphase II oocyte chromosomes

Abstract

Methylmercury (MM) denatures DNA and can induce chromosomal aberrations. In addition, it destroys microtubules and increases the incidence of aneuploidy and mitotic arrest. Although MM is distributed to gonads, data relating the cytogenetic effects of MM on mammalian germ cells in vivo have not been found. To determine whether MM increases the incidence of cytogenetic damage in oocytes, Syrian hamsters were divided into three groups: (1) negative controls; (2) positive controls, 0.25 mg Trenimon (T)/kg; and (3) 10 mg methylmercury chloride (MMC)/kg. Superovulation was utilized and metaphase II oocytes analyzed for numerical and structural chromosome aberrations. A highly significant (P = .015, Fisher's exact test) difference in the incidence of hyperploid (N = 23) oocytes was obtained between negative controls (0/150) and the MMC group (6/ 150). The incidence of hypoploid (N = 21) oocytes in negative controls and the MMC group was 12/150 and 21/150, respectively (P = .069). Structural aberrations were not observed. Of 281 oocytes analyzed in the T group, 42.7% had structural aberrations. These results primarily indicate that MMC increases the incidence of hyperploidy and not structural aberrations.