Effect of hypoxia and/or cold stress on plasma and brain amino acids in rat.

The effect of hypoxia, cold and hypoxic-cold stress was studied on plasma and brain amino acid levels of rats. Hypoxia caused a considerable increase in plasma taurine and phosphoserine levels, while the remaining amino acids (except valine, cystine, iso-leucine, leucine and anserine) decreased significantly. On the other hand cold stress significantly increased the plasma taurine, asparagine and decreased glutamine, glycine, alanine, methionine and histidine levels. The hypoxic-cold stress combination produced marked decrease in most of the plasma levels of amino acids (except phosphoserine, taurine and anserine). During brain amino acid studies, hypoxia significantly elevated taurine, aspartic acid, valine and leucine levels while the concentrations of other amino acids were not significantly altered. Cold stress was found to elevate taurine and valine levels, while leucine and phenyl-alanine levels were significantly decreased. Exposure of animals to hypoxic-hypothermia affected significantly the brain levels of valine, methionine, leucine and arginine. Since, the change in amino acid levels in brain is less prominent, as compared with plasma, in response to stress, it appeared that brain possesses higher adaptive mechanisms to counteract the stress induced amino acid level imbalance.