The Effects of Nicotine Administration on Deciduoma Induction in the Rat1

Abstract

S.c. injection of nicotine impaired decidualization in pseudopregnant rats. Dosages of 0.5 or 5.0 mg nicotine/kg body wt were administered twice daily either throughout or during different periods of pseudopregnancy. Decidualization was induced by intraluminal instillation of 0.1 ml of 0.1 M sodium phosphate buffer at various times during days 3, 4 and 5 and the resulting decidual cell response assessed by weighing each uterine horn on day 9. In control animals, a peak of responsivity occurred at 1800 h of day 4. At that time a mean response of 2120.9 .+-. 193 mg/uterine horn was obtained in comparison to responses of 1087 .+-. 351.5 mg and 992.8 .+-. 345 mg at 1600 and 2200 h, respectively. A significant reduction (P < 0.01) in the peak of responsivity occurred when the 5.0 mg dosage of nicotine was administered from day 0-9 (840.5 .+-. 325.8 mg) or from day 0-4 (1103.3 .+-. 659 mg). Rats receiving the 0.5 mg dosage of nicotine also showed a significant decrease (P < 0.01) in response when uteri were traumatized at 1800 h of day 4. Responses lower than, but not statistically different from control values were obtained when nicotine in either dosage was administered only during the proestrus and estrus preceeding pseudopregnancy or during days 5-9 of pseudopregnancy. Nicotine exerts its greatest inhibitory effect during the 1st 4 days of pseudopregnancy when uterine sensitivity to decidualization is developing.