[A comparative study of free amino acid levels in serum and cerebral cortex in uremic rat].
The etiology of uremic encephalopathy remains largely unknown. In order to elucidate the role of amino acid changes in uremic encephalopathy, the free amino acids in serum and cerebral cortex were measured in the experimental uremic models. The rats weighing 200 g underwent bilateral ureteral ligation for 48 hours (acute uremia), while the other animals were kept for 4 months after unilateral nephrectomy followed by partial 2/3 nephrectomy of the remaining kidney (chronic uremia). They were confirmed to develop chemical changes compatible with uremia showing markedly elevated serum levels of BUN, creatinine and K+, and were compared with the sham-operated controls. The amino acid patterns, obtained from serum and cerebral cortex, were essentially identical in both acute and chronic uremia. In serum, aspartic acid, glycine and 3-methylhistidine were significantly elevated, and in addition citrulline, alpha-aminoadipic acid, cystine and gamma-aminobutyric acid specifically appeared in uremia. On the contrary, glutamic acid, leucine, lysine, tryptophan, tyrosine and valine were significantly reduced. Tyrosine/phenylalanine ratio, valine/glycine ratio, essential amino acids/non essential amino acids ratio were also apparently reduced in uremia. In cerebral cortex, aspartic acid, glutamine, glycine, histidine, ornithine, phenylalanine, phosphoethanolamine and taurine were significantly elevated, whereas 1-methylhistidine and 3-methylhistidine were specifically detected. Carnocine, glutamic acid and ornithine disclosed a significant reduction in uremia. The above complicated changes in cerebral cortex could not be explained simply by the enhanced permeability of the blood-brain barrier, or by the accelerated ammonia fixation. Therefore, it was suggested that the amino acid levels in cerebral cortex vary under the control of the sophisticated mechanism.
D000596:Amino Acids / Q000097:blood / Q000378:metabolism*; D000818:Animals; D001806:Blood Urea Nitrogen; D001812:Blood-Brain Barrier; D002118:Calcium / Q000097:blood; D002540:Cerebral Cortex / Q000378:metabolism*; D003404:Creatinine / Q000097:blood; D008297:Male; D011188:Potassium / Q000097:blood; D051381:Rats; D011919:Rats, Inbred Strains; D014511:Uremia / Q000097:blood / Q000378:metabolism*
D000596:Amino Acids; D003404:Creatinine; D011188:Potassium; D002118:Calcium