In Vitro Inhibition of Human Sperm Creatine Kinase by Nicotine, Cotinine and Cadmium, as a Mechanism in Smoker Men Infertility

Background: Nicotine, cotinine and cadmium are harmful components of cigarettes that have an effect on human reproductive function. Although the effects of cigarette smoke on male reproductive function is characterized in several articles its mechanism of action is still unknown. In the present study, we investigate the effect of nicotine, cotinine and cadmium on human sperm creatine kinase activity in vitro. Materials and Methods: Total creatine kinase activity is measured in sperm homogenates after chromatography on a diethylaminoethyl cellulose (DEAE-32) column. Results: We show that creatine kinase activity is significantly inhibited by nicotine (44%), cotinine (39%) and cadmium (65%) at a concentration of 60 ?g/ml. Kinetic studies reveal that the inhibitory effect of nicotine, cotinine and cadmium are competitive in relation to creatine phosphate. Conclusion: Considering the importance of creatine kinase activity for normal sperm energy metabolism, our results suggest that inhibition of this enzyme by nicotine, cotinine and cadmium may be an important mechanism in infertility amongst male smokers. However, further investigations are needed to elucidate the exact mechanism of cigarette effect on male reproductive function at the molecular level.