Anti-stress and adaptogenic activity of L-arginine supplementation

In the present study, oral supplementation of L-arginine in rats was evaluated for its anti-stress and adaptogenic activity using the cold (5 degrees C)-hypoxia (428 mmHg)-restraint (C-H-R) animal model. A dose-dependent study of L-arginine was carried out at doses of 12.5, 25.0, 50.0, 100.0, 200.0 and 500.0 mg/kg body weight, administered orally 30 min prior to C-H-R exposure. The time taken by the rat to attain a rectal temperature of 23 degrees C (T-rec 23 degrees C) during C-H-R exposure and its recovery to Trec 37 degrees C at normal atmospheric pressure and 32 +/- 1 degrees C were used as biomarkers of anti-stress and adaptogenic activity. Biochemical parameters related to lipid peroxidation, anti-oxidants, cell membrane permeability, nitric oxide and stress, with and without administration of the least effective L-arginine dose, were measured in rats on attaining T-rec 23 degrees C and Trec 37 degrees C. The least effective adaptogenic dose of L-arginine was 100.0 mg/kg body weight. The C-H-R exposure of control rats, on attaining Trec 23 degrees C, resulted in a significant increase in plasma malondialdehyde (MDA), blood lactate dehydrogenase (LDH) and a decrease in blood catalase (CAT) and plasma testosterone levels. On recovery (T-rec 37 degrees C) of control rats, there was a further decrease in CAT and plasma testosterone, and an increase in LDH. L-Arginine supplementation resulted in a significant decrease in plasma MDA, an increase in blood superoxide dismutase ( SOD), CAT levels maintained at control values and a lower increase in LDH compared with controls (45.3 versus 58.5% and 21.5 versus 105.2%) on attaining T-rec 23 degrees C during C-H-R exposure and on recovery to Trec 37 degrees C. The results suggested that L-arginine possesses potent anti-stress activity during C-H-R exposure and recovery from C-H-R-induced hypothermia.