Enhancement of pro-oxidant effect of 7,12-dimethylbenz (a) anthracene (DMBA) in rats by pre-exposure to restraint stress

The current study was designed to assess the effect of immobilization stress on liver toxicity induced by topical as well as oral administration of 7,12-dimethyl benz(a)anthracene (DMBA) in Swiss Albino rats. The experimental animals were divided into six groups. Group 1 animals were exposed to chronic restraint stress alone for 10 days (3 h/day), shaved back of animals in group II were painted with 0.5% solution of DMBA twice a week for 4 weeks. Group III animals were first exposed to restraint stress similar to group I followed by DMBA application as in group II, group IV animals were orally administered four doses of 0.5% DMBA solution. (1 ml/rat) at weekly intervals, while group V animals were first exposed to restraint stress as in group I followed by oral dose of DMBA similar to group IV. The untreated Group VI animals served as controls. Rats were sacrificed after a period of 4 weeks following DMBA administration. Biochemical measurements were carried out on liver tissues and serum/plasma of control and treated animals. Restraint stress was found to have marked effect on DMBA induced alteration of liver function as revealed by the increase in tissue marker enzymes viz glutamate oxaloacetate transaminase (GOT), glutamate pyruvate transaminase (GPT), alkaline phosphatase (ALP), acid phosphatase (ACP), lactate dehydrogenase (LDH) with a significant further decrease in antioxidant enzymes catalase (CAT), superoxide dismutase (SOD), glutathione-S-transferase (GST), glutathione reductase (GR) as compared to controls and DMBA alone(topical/oral) or stress alone treated rats. Increased lipid peroxidation was accompanied by a significant decrease in the level of total reduced glutathione (GSH). The changes in the levels of marker enzymes and in vivo antioxidants in serum/plasma were comparable to that of liver. The results of the present study indicate that immobilization stress markedly enhances DMBA induced alteration of liver and circulatory antioxidant status of the rats irrespective of the mode of DMBA administration though with a predominant effect on orally infused DMBA.