Effects of nicotine on oviducal blood flow and embryo development in the rat.

Nicotine (5.0 mg/kg) was injected (s.c.) twice daily on Day 1 or Days 1-4 or 1-5 of pregnancy. Cumulative doses of nicotine retarded embryo cell cleavage and substantially reduced embryo cell number (saline vs nicotine: 42.5 +/- 1.7 vs 22.1 +/- 1.9 nuclei/embryo, at 12:00 h on Day 5; P less than 0.05). However, treatment for even 1 day (Day 1) significantly reduced cell number (saline vs nicotine: 42.5 +/- 1.7 vs 30.5 +/- 0.9, at 12:00 h day on Day 5; P less than 0.01). Nicotine injection also resulted in a marked and prolonged reduction in oviduct blood flow (pretreatment vs 90 min after nicotine: 0.61 +/- 0.06 vs 0.37 +/- 0.10 ml/min . g-1; P less than 0.005). The results indicate that, in the rat, even a brief exposure to nicotine, the chief alkaloid of tobacco, reduces oviducal blood flow and the rate of embryo cell proliferation. The embryo is therefore susceptible to the effects of nicotine before implantation.