Cadmium and assisted reproductive technologies: relevance to public health

Abstract

OBJECTIVE: Prior studies suggest that cadmium (Cd) may adversely affect sperm through a pro-oxidant mechanism generating reactive oxygen species (ROS) and oxidative stress. Infertile men have been shown to have higher levels of ROS. We tested the hypothesis that men requiring ICSI have increased Cd exposure. DESIGN: Analysis of the relationship between semen parameters, seminal plasma metal levels and fertilization rates among male partners of infertile couples undergoing ICSI (n =20; w/ varicoceles (VX], n=7) and dose-compensated IVF inseminations (n=96; w/ VX, n=16) during the period 2/95 to 8/96. MATERIALS AND METHODS: Sperm concentration and motility were determined in duplicate specimens using WHO criteria and acrosome morphology was assessed in fixed, unstained sperm. Seminal plasma Cd, lead (Pb) and zinc (Zn) levels were quantified by atomic absorption. Fertilization rates were defined by standard protocols. RESULTS: Sperm concentration, motility, morphology and fertilization rates were all reduced in ICSI patients as compared to IVF (P<0.01). Although Zn and Pb levels did not differ between the two groups, Cd was significant elevated in ICSI patients as compared to IVF (P<0.004). ICSI fertilization was positively correlated with sperm motility (Spearman correlation [SC], r=0.38, P<0.05) and Zn (SC, r=0.73, P<0.001). The proportion of men with VX treated with ICSI was higher than those treated with IVF (35% vs. 17%). In the ICSI group, Cd was higher in subjects with VX than without VX (P<0.02) or with VX treated with IVF (P<0.003). CONCLUSIONS: The data suggest that seminal plasma Cd levels are elevated in men requiring ICSI, with or without VX. Both sperm motility and seminal plasma Zn levels positively correlated with ICSI fertilization rates. Cd may increase sperm ROS production with associated sperm membrane damage and decreased motility. Zn has the potential to be an inexpensive therapeutic antioxidant.