Protective effects of progesterone on implantation failure induced by dibutyltin dichloride in rats

We previously showed that dibutyltin dichloride (DBTCl) at 7.6 mg/kg and higher on days 0-3 of pregnancy caused implantation failure and a decline in serum progesterone levels in rats and hypothesized that the decline is responsible for the implantation failure. This study was conducted to determine the protective effects of progesterone on the DBTCl-induced implantation failure in rats. Rats were given oral DBTCl at 0, 7.6, or 15.2 mg/kg on days 0-3 of pregnancy and/or subcutaneous progesterone at 2 mg/rat on days 0-8 of pregnancy. The reproductive outcome was determined on day 9 of pregnancy. No effects of administration of progesterone alone on the pregnancy rate and number of implantations were found. The pregnancy rate and number of implantations were significantly decreased after administration of DBTCl alone. The pregnancy rate and number of implantations were higher in the groups given DBTCl and progesterone than the groups given DBTCl alone. The present data indicate that progesterone protects, at least in part, against the DBTCl-induced implantation failure and support our hypothesis that the decline in progesterone levels is a primary mechanism for the implantation failure due to DBTCl.