Branched-chain transaminase and keto acid dehydrogenase activities in burned rats: evidence for a differential adaptation according to sex.

Female and male rats show differences in nitrogen metabolism after trauma, and the contribution of the branched-chain amino acid oxidizing pathway following thermal injury was evaluated. Female and male rats were subdivided into baseline, burned and unburned, pair-fed groups. Burned and pair-fed rats were sacrificed on days 1, 2, and 3 postburn, and branched-chain amino acid transaminase (BCTA), branched-chain alpha-keto acid dehydrogenase (BCKDH) activated and total, and succinate dehydrogenase (SDH) activities were measured in red and white muscle and in liver, BCTA was not measured in liver. Baseline and pair-fed groups had similar enzyme activities. Changes following thermal injury were: (1) elevated SDH in all tissues for both sexes; (2) increased BCTA activity in red and white muscles from male rats; and (3) increased percentage of activated BCKDH in red and white muscles on days 2 and 3 for male rats. All other activities were unchanged. These findings agree with previous post trauma differences in urinary nitrogen losses in female and male rats. The results show that the enzymes for oxidation of the branched-chain amino acids in males respond to injury while those do not in females.