Effect of nickel sulfate on testicular steroidogenesis in rats during protein restriction

Nickel, a widely used heavy metal, exerts potent toxic effects on peripheral tissues as well as on the reproductive system. Low dietary protein coupled with exposure to this metal induces more severe changes, including biochemical defects, structural disorders, and altered physiologic functions. This study was designed to assess the effects of nickel sulfate on testicular steroidogenesis and to ascertain whether such alterations are reversible with normal protein and protein-restricted dietary regime. Nickel sulfate [2 mg/100 g body weight (bw)] dissolved in double-distilled water was administered on alternate days for 10 doses in a normal protein diet (18% casein) and a protein-restricted diet (5% casein) to Wistar male albino rats (bw 160 +/- 5 g). Two groups, one with a normal protein diet and the other with a protein-restricted diet, served as controls. Twenty-four hours after the last treatment, all the animals except those in withdrawal groups were sacrificed by decapitation. We observed a significant reduction in the activities of the testicular steroidogenic enzymes and plasma testosterone concentration accompanied by a significant elevation in cholesterol and ascorbic acid level in both dietary groups. After 15 days of withdrawal from the nickel sulfate treatment, the testicular steroidogenic enzymes, along with plasma testosterone level, improved significantly in both normal protein-fed and protein-restricted dietary groups. The effects of nickel on testicular cholesterol and ascorbic acid concentration were also reduced after withdrawal. Our results indicate that nickel sulfate affects the steroidogenic enzymes, causing alteration in the formation of testosterone in both dietary groups, which was manifested in the elevated cholesterol and ascorbic acid level with decreased activities of steroidogenic enzymes in adult rats testes. However, these alterations were reversible in both groups of animals fed normal protein diets and protein-restricted diets.