1 Shao-Chin.indd

Cigarette smoke is known to be a serious health risk factor and considered reproductively toxic. In the current study, we investigated whether constituents of cigarette smoke, pyrazine, 2-ethylpyridine, and 3-ethylpyridine, adversely aff ect reproductive functioning such as oocyte maturation and sperm capacitation. Our fi ndings indicated that three smoke components were involved in retardation of oocyte maturation in a dose-dependent manner and the lowest-observed-adverse-eff ect level (LOAEL) was determined to be 10-10M. However, individual smoke components administrated at the LOAEL did not attenuate oocyte maturation, demonstrating that all three toxicants were equally required for the observed growth impairment. When exposed to all three components at 10-10M during in vitro capacitation, murine sperm lost forward progression and were unable to show adequate hyperactivation, which is indicative of the incompletion of the capacitation process. Only sperm administrated with 3-ethylpyridine alone showed signifi cant reduction in capacitation status, suggesting the chemical is the one responsible for disrupting sperm capacitation. Taken together, this is the fi rst report that documents the eff ect of cigarette smoke components on oocyte maturation and sperm capacitation. The present fi ndings demonstrate the adverse eff ects of smoke constituents of mammalian reproduction and the diff erences in sensitivity to smoke components between male and female gametes. Since both processes take place in the female reproductive system, our data provide new insights into deleterious consequences of maternal exposure to cigarette smoke.