Parimal Chowdhury1, Michael Soulsby, Kyongmin Kim. 1. Department of Physiology and Biophysics, University of Arkansas for Medical Sciences, 4301 W. Markham St., Little Rock, AR 72205, USA. PChowdhury@uams.edu
Abstract
INTRODUCTION: An improvement in the imbalance in the oxidant-antioxidant defense system would lessen the severity of any oxidative stress documented during or after spaceflight. In this study, we investigated the effects of a 14-d hind limb unloading (HLU) of rats on the formation of malondialdehyde (MDA), an oxidative biomarker and also an end-product of lipid peroxidation, in tissues and blood of rats. L-carnitine, a well-known enhancer of activities of the mitochondrial antioxidant system, was used to confirm the HLU-induced oxidative response. METHODS: Three groups of rats were used in the current study. Group 1 was a control group that was maintained on drinking water only; Groups 2 and 3 were unloaded HLU groups that were maintained on drinking water and on L-carnitine in drinking water, respectively. RESULTS: Our results showed that rats that were hind limb unloaded but maintained on water only showed enhanced levels of tissue MDA when compared with the paired hind limb loaded controls. Animals hind limb unloaded but maintained on L-carnitine in their drinking water had no increase in their tissue MDA levels when compared with the loaded controls, but their MDA levels were significantly reduced from the HLU group, p < 0.05. DISCUSSION AND CONCLUSIONS: These data indicate that HLU induced an oxidative response in rats and this response was absent in the presence of L-carnitine. The results of our study implicate the potential application of antioxidants as a useful dietary source in astronauts living in a stressful environment.
INTRODUCTION: An improvement in the imbalance in the oxidant-antioxidant defense system would lessen the severity of any oxidative stress documented during or after spaceflight. In this study, we investigated the effects of a 14-d hind limb unloading (HLU) of rats on the formation of malondialdehyde (MDA), an oxidative biomarker and also an end-product of lipid peroxidation, in tissues and blood of rats. L-carnitine, a well-known enhancer of activities of the mitochondrial antioxidant system, was used to confirm the HLU-induced oxidative response. METHODS: Three groups of rats were used in the current study. Group 1 was a control group that was maintained on drinking water only; Groups 2 and 3 were unloaded HLU groups that were maintained on drinking water and on L-carnitine in drinking water, respectively. RESULTS: Our results showed that rats that were hind limb unloaded but maintained on water only showed enhanced levels of tissue MDA when compared with the paired hind limb loaded controls. Animals hind limb unloaded but maintained on L-carnitine in their drinking water had no increase in their tissue MDA levels when compared with the loaded controls, but their MDA levels were significantly reduced from the HLU group, p < 0.05. DISCUSSION AND CONCLUSIONS: These data indicate that HLU induced an oxidative response in rats and this response was absent in the presence of L-carnitine. The results of our study implicate the potential application of antioxidants as a useful dietary source in astronauts living in a stressful environment.