The Effects of Nicotine on Implantation in the Rat1

Abstract

The effects of nicotine on blastocyst implantation were investigated in the rat. Flushing each uterine horn with a constant force and volume of saline at selected times during pregnancy demonstrated that, in control animals, implantation progressed sufficiently by 1200 h of day 5 (day 0 = day of insemination) to prevent conceptus retrieval. In animals receiving twice daily s.c. injections of nicotine (5 mg/kg body per injection), blastocysts could be retrieved as late as 2100 h of day 5. In nicotine-treated rats, the development of blastocyst attachment sufficient to resist flushing was delayed approximately 9 h. Simultaneous entrance of fertilized ova into the uterine lumen at 1800 h of day 3 in both control and nicotine-treated animals demonstrated that this delay could not be attributed to altered transport through the oviduct. Associated with the altered time course of implantation in nicotine-treated rats were changes in blastocyst development; the time of zona pellucida loss and the growth of the inner cell mass were delayed. The number of blastocysts ultimately implanting in nicotine-treated animals did not differ from that of controls.