Welbourne T C, Givens G, Joshi S
Department of Physiology and Biophysics, Louisiana State University Medical Center, Shreveport 71130.
Am J Physiol. 1988 Jan;254(1 Pt 2):F134-8. doi: 10.1152/ajprenal.1988.254.1.F134.
Adrenalectomized (ADX) animals exhibit a blunted renal response to chronic acid loading. To determine whether this response truly reflects impaired renal ammoniagenesis from glutamine, urinary ammonium excretion was compared with acid intake in ADX, intact, and ADX rats supplemented with either a low dose (4 micrograms.100 g-1.day-1) or a high dose (40 micrograms.100 g-1.day-1) of triamcinolone. ADX rats consumed similar amounts of acid as did intact controls yet excreted only 37% of the load as ammonium; in contrast intact controls returned 86% and triamcinolone-supplemented animals returned 98 and 88% for low and high doses, respectively. Nor could the reduced ammonium excretion be attributed to increased renal venous release, since total ammonia production, the sum of renal venous and urine ammonium, was reduced to 49% of the intact controls; low- and high-dose triamcinolone restored and markedly increased the production rate. Underlying the impaired ammonia production rate in ADX rats was a reduced rate of glutamine extraction, 350 +/- 49 vs. 896 +/- 102 and 1,260 +/- 247 and 1,448 +/- 112 nmol.min-1.100 g-1 for intact and low and high doses, respectively. Unlike intact acidotic and glucocorticoid-supplemented ADX acidotic rats, glutamine extraction was disassociated from the delivered glutamine load consonant with the role of glucocorticoid in coupling cellular glutamine transport to its metabolic utilization.
肾上腺切除（ADX）的动物对慢性酸负荷的肾脏反应减弱。为了确定这种反应是否真的反映了谷氨酰胺生成氨的能力受损，我们比较了ADX大鼠、完整大鼠以及补充低剂量（4微克·100克⁻¹·天⁻¹）或高剂量（40微克·100克⁻¹·天⁻¹）曲安西龙的ADX大鼠的尿铵排泄量与酸摄入量。ADX大鼠摄入的酸量与完整对照组相似，但铵排泄量仅为负荷量的37%；相比之下，完整对照组的铵排泄量为86%，补充曲安西龙的动物低剂量组和高剂量组分别为98%和88%。铵排泄减少也不能归因于肾静脉释放增加，因为总氨生成量（肾静脉氨和尿铵之和）降至完整对照组的49%；低剂量和高剂量曲安西龙恢复并显著提高了生成率。ADX大鼠氨生成率受损的根本原因是谷氨酰胺提取率降低，完整大鼠、低剂量组和高剂量组分别为350±49、896±102、1260±247和1448±112纳摩尔·分钟⁻¹·100克⁻¹。与完整的酸中毒大鼠和补充糖皮质激素的ADX酸中毒大鼠不同，谷氨酰胺提取与输送的谷氨酰胺负荷脱节，这与糖皮质激素在将细胞谷氨酰胺转运与其代谢利用相偶联中的作用一致。
