Effect of tamoxifen on sperm fertilising ability and preimplantation embryo development

Recent evidences point to a role of estrogens in males. We have earlier reported that tamoxifen, a synthetic non-steroidal antiestrogen, when administered to adult male rats, in the dose range of 0.04-0.4 mg/kg per day, reduced fertility. The reduced fertility was measured in terms of fertility index (a measure of the efficiency of the ovulated ovas to fertilise and implant), fecundity (siring ability) and litter. size. The present study was done to investigate whether the reduction in fertility index was due to reduction in fertilising ability or increase in pre-implantation embryo loss. Also a dose related effect of tamoxifen from 0.02 mg to 2 mg/kg per day on the fertility of rhc male rats was studied. To study the fertilising ability, control and tamoxifen (0.4 mg/kg per. day, the most effective dose) treated adult male rats were mated with normal cycling females and the females sacrificed at day 0-4 of gestation. Eggs fertilised/unfertilised were flushed from the oviduct/uterus and the number and types of eggs were noted. The index of fertilisation, a measure of the fertilising ability was determined. The studies demonstrate that the reduction in fertility is not due to decreased fertilising ability but because of the increased pre-implantation embryo loss as evident from an increase in number of abnormal eggs in the treated group with no change in index of fertilisation. A dose related decrease in fertility was observed. The present study suggests that tamoxifen at 0.02-2-mg dose is predominantly estrogenic in males and paternal factor/s sensitive to tamoxifen is involved in embryogenesis. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.