May R C, Hara Y, Kelly R A, Block K P, Buse M G, Mitch W E
Am J Physiol. 1987 Jun;252(6 Pt 1):E712-8. doi: 10.1152/ajpendo.1987.252.6.E712.
Branched-chain amino acid (BCAA) metabolism is frequently abnormal in pathological conditions accompanied by chronic metabolic acidosis. To study how metabolic acidosis affects BCAA metabolism in muscle, rats were gavage fed a 14% protein diet with or without 4 mmol NH4Cl X 100 g body wt-1 X day-1. Epitrochlearis muscles were incubated with L-[1-14C]-valine and L-[1-14C]leucine, and rates of decarboxylation, net transamination, and incorporation into muscle protein were measured. Plasma and muscle BCAA levels were lower (P less than 0.05) in acidotic rats. Rates of valine and leucine decarboxylation and net transamination were higher (P less than 0.05) in muscles from acidotic rats; these differences were associated with a 79% increase in the total activity of branched-chain alpha-keto acid dehydrogenase and a 146% increase in the activated form of the enzyme. We conclude that acidosis affects the regulation of BCAA metabolism by enhancing flux through the transaminase and by directly stimulating oxidative catabolism through activation of branched-chain alpha-keto acid dehydrogenase.
在伴有慢性代谢性酸中毒的病理状态下，支链氨基酸（BCAA）代谢常常异常。为研究代谢性酸中毒如何影响肌肉中的BCAA代谢，给大鼠灌胃14%蛋白质饮食，其中一组添加4 mmol NH₄Cl×100 g体重⁻¹×天⁻¹，另一组不添加。将肱三头肌与L-[1-¹⁴C]-缬氨酸和L-[1-¹⁴C]亮氨酸一起孵育，测量脱羧率、净转氨率以及掺入肌肉蛋白的速率。酸中毒大鼠的血浆和肌肉BCAA水平较低（P<0.05）。酸中毒大鼠肌肉中的缬氨酸和亮氨酸脱羧率及净转氨率较高（P<0.05）；这些差异与支链α-酮酸脱氢酶的总活性增加79%以及该酶的活性形式增加146%有关。我们得出结论，酸中毒通过增强转氨酶通量以及通过激活支链α-酮酸脱氢酶直接刺激氧化分解代谢来影响BCAA代谢的调节。
