Low blood Pb levels could adversely affect the pro-oxidant balance in rat epididymides

Introduction: The impairment of male fertility, identified in epidemiological studies in recent decades, may be associated with increasing exposure to environmental factors, among which heavy metals, especially lead (Pb), have a unique role due to their prevalence and toxicity. The aim of the study was to determine the effect of Pb on the epididymis, an organ in which spermatozoa reach  maturity and acquire the ability to fertilize an egg. In particular, it was investigated whether low blood Pb levels could adversely affect the pro-oxidant/antioxidant balance in rat epididymides.

Materials and methods: The intensity of oxidative stress was measured by changes in lipid peroxidation (by chemiluminiscence method), as well as in protein expression and the activity of superoxide dismutase (SOD) and catalase (CAT). Additionally, it was investigated whether the toxic effects of Pb could be alleviated by the simultaneous administration of the antioxidants – tocopherol (vitamin E) or its water-soluble counterpart Trolox.

Results: Chronic exposure to Pb resulted in increased lipid peroxidation in the epididymis (manifested by a marked intensification in chemiluminescence from the caput and cauda epididymis). Significantly, when Pb-treated rats were also supplemented with Trolox or tocopherol, the increase in chemiluminiscence intensity was significantly lower, which indicated the beneficial effect of these antioxidants on reduction of Pb-induced oxidative stress. However, a direct beneficial effect of supplementation on the activity and expression of SOD and CAT was not demonstrated.The activity and expression of SOD was not affected by exposure to Pb or to simultaneous administration of antioxidants. The use of tocopherol and Trolox had also no beneficial effect on the Pb-induced reduction in the activity and expression of CAT.

Conclusions: The environmental Pb-exposure leading to metal accumulation in whole blood at  oncentrations below the “threshold level” (5 μg/dL) may cause disruption in the prooxidant/antioxidant balance in rat epididymides containing epididymal spermatozoa.