The effect of zinc supplementation on the effects of lead on the rat testis

Abstract

With increasing concerns about environmental pollution, the interaction of micronutrients with toxic metals is of great interest. The present study was designed to investigate testicular effects of lead following concomitant administration of zinc. Lead was administered orally as lead acetate (50 mg/kg b.w.) daily for 3 months to male Portan rats with or without zinc (1 mg/kg b.w. as zinc sulphate). The control group was given the same volume of distilled water. Endpoints included lead concentration in various body organs as well as in the reproductive system, including testicular subfractions; the testicular enzymes superoxide dismutase (SOD) and catalase; the marker enzyme δ-aminolevulinic acid dehydratase (δ-ALAD); and testicular histoarchitecture. The concentrations of lead in bone, kidney, prostate, testis, liver, epididymis, spleen, seminal vesicles, and blood were significantly higher in lead-treated rats. Lead deposition was reduced in animals that received supplemental zinc. There was a 30% reduction in lead deposition in the testis when zinc was coadministered. At the subcellular level, there was differential accumulation of lead; the nucleus preferentially took up the metal after lead treatment alone, while zinc coadministration shifted lead accumulation to the mitochondria. A significant decrease in δ-ALAD and in SOD activity was seen in the testis with lead treatment. Coadministration of zinc prevented these decreases, at least partially. Zinc coadministration did not prevent the inhibition of catalase observed with lead treatment. Histologically, the alterations in the testis with lead treatment alone were more pronounced compared to animals in which zinc was supplemented. Improvement in the inhibition of δ-ALAD and in the ubiquitous cellular enzyme SOD suggests less testicular tissue damage due to detoxification of free radicals. In conclusion, zinc supplementation ameliorates lead-induced testicular damage both at the cellular and subcellular level. The protective effect may be due to differential distribution of lead, either because of competition between lead and zinc or displacement of lead by zinc.