Effect of chemicals on the duration of male meiosis in mice detected with laser scanning cytometry

Aneuploidy studies in sperm such as the sperm-FISH assay require a precise knowledge of the duration of spermatogenesis, especially of the meiotic stages. This is important in order to sample sperm from the epididymis at appropriate intervals after animal treatment. However, aneugens may delay the cell cycle. The progression from meiotic divisions to epididymal sperm was determined by labelling the last S-phase before meiosis with the thymidine analogue 5-bromo-2'-deoxyuridine (BrdU) and treating the animals 13 days later with the test chemicals. In a time frame of 20-24 days after treatment, BrdU-containing sperm were identified with a FITC-labelled anti-BrdU antibody and green fluorescent sperm were scored with a laser scanning cytometer (LSC). We studied the effects of the chemicals acrylamide, colchicine, diazepam, griseofulvin, taxol, thiobendazole, trichlorfon and vinblastine on the duration of meiotic divisions in male mice. Colchicine treatment prolonged the duration of meiotic divisions by about 48 h. On days 21 and 22, the frequencies of BrdU-labelled sperm in the colchicine group were 11.7 and 9.4%, respectively, while they were 28.4 and 30.6%, respectively, in the concurrent controls (P > 0.01). On day 24 after treatment, the frequency of labelled sperm in the colchicine group reached the control level. Etoposide treatment resulted in an elevation of BrdU-labelled sperm at 23 rather than 22 days. The other chemicals showed no significant effect of prolonging meiotic cell cycle progression. On the basis of the colchicine and etoposide data, it is suggested that the effect of a chemical on the meiotic cell cycle progression is determined first in order to chose the appropriate sperm sampling time to detect aneuploidy induction.