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Nicotine, but not cotinine, has a direct toxic effect on ovarian function in the immature gonadotropin-stimulated rat
C W Blackburn1, C A Peterson, H A Hales
1Department of Obstetrics and Gynecology, University of Utah School of Medicine, Salt Lake City 84132.
Abstract:
PMSG-primed and hCG-triggered rat ovaries were exposed to nicotine and its major metabolite, cotinine, using in vitro and in vivo experimental approaches. In vivo, a dose-dependent reduction in oocytes within the fallopian tube was noted in nicotine treated rats (6.25 ng/g animal weight, P < 0.001). Serum estradiol concentrations were also reduced in rats receiving nicotine (P < 0.04). There were no significant differences in weight gain. Cotinine had no effects. In vitro, nicotine also caused a dose-dependent reduction in oocytes in the collection chamber (P < 0.0001). Estradiol levels in nicotine-treated perfusions were reduced and reached statistical significance at 7 h (P < 0.003). The in vitro fertilization rate was reduced for nicotine-treated perfusions exposed to 1.43 pg/mL of nicotine (P < 0.001). Cotinine had no effect in vitro. We conclude that nicotine inhibits ovulation, estradiol production, and fertilization both in vivo and in vitro in rat models of ovulation. Cotinine did not affect these parameters. These effects of nicotine are notably independent of nicotine's known effect on the midcycle gonadotropin surge.
Insights
Nicotine exposure in rats significantly reduced oocytes, estradiol levels, and fertilization rates in both live animals and in vitro. This reproductive inhibition by nicotine occurred independently of its effects on hormone surges, while its metabolite cotinine showed no impact.
Area of Science:
- Reproductive Biology
- Toxicology
- Endocrinology
Background:
- Nicotine is a widely consumed substance with known health implications.
- The impact of nicotine on ovulation and reproductive parameters requires further elucidation.
- Understanding nicotine's effects is crucial for reproductive health assessments.
Purpose of the Study:
- To investigate the effects of nicotine and cotinine on ovulation, estradiol production, and fertilization in a rat model.
- To determine if nicotine's effects on ovulation are independent of gonadotropin surge modulation.
- To compare the effects of nicotine versus its metabolite, cotinine.
Main Methods:
- Utilized both in vivo and in vitro experimental approaches in PMSG-primed and hCG-triggered rats.
- Administered nicotine and cotinine at specific doses to assess effects on oocyte count, serum estradiol, and fertilization rates.
- Measured oocyte recovery, estradiol concentrations in serum and perfusions, and in vitro fertilization rates.
Main Results:
- In vivo, nicotine caused a dose-dependent reduction in oocytes and serum estradiol.
- In vitro, nicotine reduced oocyte recovery and fertilization rates, with decreased estradiol levels observed.
- Cotinine demonstrated no significant effects on any measured reproductive parameters in either experimental model.
Conclusions:
- Nicotine inhibits ovulation, estradiol production, and fertilization in rat models, both in vivo and in vitro.
- These inhibitory effects of nicotine are independent of its influence on the midcycle gonadotropin surge.
- Cotinine does not appear to possess the same reproductive inhibitory properties as nicotine.
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