ADVERSE-EFFECTS OF CYCLOPHOSPHAMIDE ON PROGENY OUTCOME CAN BE MEDIATED THROUGH POSTTESTICULAR MECHANISMS IN THE RAT

Previous studies from our laboratory have suggested that, in addition to an effect on spermatozoa in the testis, cyclophosphamide may have an adverse effect on spermatozoa after they leave the testis, during epididymal transit. To elaborate on this post-testicular effect on germ cells and to determine at which site(s) in the epididymis germ cells are most sensitive to cyclophosphamide treatment, three experiments were undertaken. First, the time course of the effect of treatment of male rats with cyclophosphamide on the outcome of their progeny was determined. Male rats were treated daily by gavage with saline or one of two doses of cyclophosphamide (6.8 mg/kg or 10.0 mg/kg) for 1, 4, or 7 days. At the end of each treatment period, males were mated to assess the effect on pregnancy outcome. No effect was observed on pre-implantation loss at any time among any of the groups, but there was a time-dependent and dose-related increase in post-implantation loss. Post-implantation loss was significantly increased after 4 days of treatment and reached nearly 40% after 7 days of drug exposure (100.0 mg/kg). Second, the effect of treatment with single high doses of cyclophosphamide was studied. Male rats were treated with a single dose of cyclophosphamide (10, 30, or 70 mg/kg) and bred 1 day and 4 days post-treatment. No significant change in pre-implantation loss was observed at either time point; no change in post-implantation loss was found after 1 day post-treatment. However, a significant increase in post-implantation loss was observed in the two high-dose groups 4 days post-treatment. Third, the effect of cyclophosphamide treatment on animals whose efferent ducts had been ligated was determined. Bilateral ligation of the efferent ducts for 7 days did not affect male progeny outcome; however, ligation followed by administration of cyclophosphamide at a dose of 10.0 mg/kg for 7 days produced the same percentage of post-implantation loss as that produced by cyclophosphamide treatment alone. Together these results demonstrate that short-term paternal treatment with cyclophosphamide (4 or 7 days) exerts an adverse effect on the progeny outcome that is mediated by a post-testicular mechanism. That 4 days are required for the adverse effect of cyclophosphamide on post-testicular spermatozoa to be manifested suggests that spermatozoa in transit through the caput epididymidis and corpus epididymidis may be more affected by cyclophosphamide than those in the cauda epididymidis.