Lipid peroxidation in rat brain is increased by simulated weightlessness and decreased by a soy-protein diet.

This study tested whether or not simulated weightlessness by tail-suspension increases the levels of lipid peroxidation products in rat brain. The brain tissues of rats on a soybean diet were also assayed for lipid peroxidation products to evaluate the possible role of soy-protein as a dietary anti-oxidant. Male Sprague-Dawley rats were used. Group 1 rats were fed standard Purina rat chow ad libidum and served as controls. Group 2 rats were fed a soybean diet containing 37% soy-protein and were not tail-suspended. Group 3 rats were fed standard Purina rat chow ad libidum and were tail-suspended to induce simulated weightlessness. After 2 wk, all of the rats were killed. Each whole brain was segmented into frontal cortex, cerebellum, and brain stem. After a specific weight of each segment was excised, the residual tissues were combined and used as a whole brain sample. The samples were analyzed for lipid peroxidation products by a chromogenic assay that reacts with malondialdehyde (MDA) and 4-hydroxyalkenals (4-HNE). The mean concentrations of lipid peroxidation products (MDA plus 4-HNE) in whole brain, frontal cortex, cerebellum, and brain stem of the control rats ranged from 16 to 18 micromol/g; the corresponding means ranged from 10 to 13 micromol/g in rats fed the soybean diet, and from 22 to 26 micromol/g in the tail-suspended rats. Thus, the mean levels of lipid peroxidation products in brain tissues were decreased in the rats fed the soy diet and were increased in the rats that were tail-suspended to simulate weightlessness, when compared to those of rats fed a regular diet.