Effect of tamoxifen on sperm fertilising ability and preimplantation embryo development

Recent evidences point to a role of estrogens in males. We have earlier rep orted that tamoxifen, a synthetic non-steroidal antiestrogen, when administ ered to adult male rats, in the dose range of 0.04-0.4 mg/kg per day, reduc ed fertility. The reduced fertility was measured in terms of fertility inde x (a measure of the efficiency of the ovulated ovas to fertilise and implan t), fecundity (siring ability) and litter. size. The present study was done to investigate whether the reduction in fertility index was due to reducti on 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, c ontrol 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 sacr ificed at day 0-4 of gestation. Eggs fertilised/unfertilised were flushed f rom the oviduct/uterus and the number and types of eggs were noted. The ind ex of fertilisation, a measure of the fertilising ability was determined. T he studies demonstrate that the reduction in fertility is not due to decrea sed fertilising ability but because of the increased pre-implantation embry o loss as evident from an increase in number of abnormal eggs in the treate d group with no change in index of fertilisation. A dose related decrease i n fertility was observed. The present study suggests that tamoxifen at 0.02 -2-mg dose is predominantly estrogenic in males and paternal factor/s sensi tive to tamoxifen is involved in embryogenesis. (C) 2001 Elsevier Science I reland Ltd. All rights reserved.