Stress-Induced Changes in Testosterone Secretion in Male Rats: Role of Oxidative Stress and Modulation by Antioxidants

Abstract

Seventy adult male albino rats were randomly allotted into 3 main groups: control group (n = 10), acute stress-exposed group (n = 30) and chronic stress-exposed group (n = 30). Each of the stressed groups was subdivided into 3 equal subgroups (n = 10/subgroup, SG): subgroup 1 animals were exposed to immobilization stress, SG2 animals, were given immobilization stress and supplemented with α-tocopherol (vitamin E), SG3 animals were exposed to immobilization stress and supplemented with ascorbic acid (vitamin C). Immobilization stress exposure was applied once for 6 continuous hours in the acute stressed group and was 6 hours daily for 10 consecutive days in the chronic stressed group. In all vitamin supplemented groups, both vitamin E and C were administered orally mixed with the diet in a similar dose of 500 mg/kg diet. This supplementation started 6 weeks prior to the stress exposure and continued throughout the experimental period. At the end of the last immobilization session, sera were harvested from all animals thereafter, animals were sacrificed and the testes were immediately excised and processed for further biochemical investigations. Serum testosterone and luteinizing hormone levels were measured and the activities of antioxidant enzymes [catalase (CAT) & glutathione-s-transferase (GST)] as well as malondialdehyde (MDA) concentrations were determined in sera and testes. Compared to control, the results revealed that acute and chronic immobilization stress caused significant decrease in levels of serum testosterone and luteinizing hormone (LH). Also, significant reductions (P < 0.01) were found in the activities of CAT and GST in sera and testes. Contrariwise, there existed a significant (P < 0.05) increase in MDA concentrations in serum and testis. Co-administration of vitamin E or C relatively restored (P < 0.01) the above parameters. Thus, this study draws a conclusion that immobilization stress of male rats significantly inhibited testosterone secretion and induced oxidative stress which partially mediated this inhibition. It also proved a protective role of vitamin E and C against the oxidative stress-induced down-regulation of testosterone secretion with a better efficacy of vitamin E.