Rodriguez-Nichols F, Laughrey E, Tannen R L
Am J Physiol. 1984 Dec;247(6 Pt 2):F896-903. doi: 10.1152/ajprenal.1984.247.6.F896.
Although chronic metabolic acidosis results in an adaptive increase in the renal capacity to produce NH3, the response to a low pH produced by chronic respiratory acidosis is unknown. Rats were placed in a specially constructed chamber with an ambient CO2 of 10% for 3 days, which increased their PCO2 to 76 +/- 4 mmHg. NH3 production was determined in vitro using both isolated kidneys perfused with 0.5 mM glutamine and cortical tubules incubated with 1 mM glutamine. Conscious rats with chronic respiratory and chronic metabolic acidosis had similar arterial pHs (7.29 +/- 0.01 and 7.31 +/- 0.01), which were significantly lower than controls (7.41 +/- 0.04). NH3 production by kidneys from rats with chronic respiratory acidosis perfused at pH 7.4 did not differ significantly from normal controls (1.13 +/- 0.13 vs. 1.07 +/- 0.17 mumol X min-1 X g-1). By contrast, kidneys from rats with chronic metabolic acidosis produced significantly more NH3 than both these groups (2.73 +/- 0.29 mumol X min-1 X g-1). Cortical tubules from rats with chronic respiratory acidosis also showed no evidence of adaptation in both NH3 (8.8 +/- 0.8 vs. 11.6 +/- 0.8 mumol X min-1 X g-1) and glucose (1.38 +/- 0.08 vs. 1.41 +/- 0.13 mumol X min-1 X g-1) production in comparison with controls, whereas chronic metabolic acidosis stimulated both ammoniagenesis and gluconeogenesis twofold or more. Thus a low systemic pH does not account for the adaptation in the capacity of the kidney to produce either ammonia or glucose.(ABSTRACT TRUNCATED AT 250 WORDS)
尽管慢性代谢性酸中毒会导致肾脏产生NH₃的能力适应性增加，但慢性呼吸性酸中毒所产生的低pH值的反应尚不清楚。将大鼠置于一个特制的环境中，环境二氧化碳浓度为10%，持续3天，这使得它们的PCO₂升高至76±4 mmHg。使用灌注0.5 mM谷氨酰胺的离体肾脏和与1 mM谷氨酰胺一起孵育的皮质肾小管在体外测定NH₃的产生。患有慢性呼吸性和慢性代谢性酸中毒的清醒大鼠具有相似的动脉pH值（分别为7.29±0.01和7.31±0.01），显著低于对照组（7.41±0.04）。在pH 7.4灌注的慢性呼吸性酸中毒大鼠的肾脏产生的NH₃与正常对照组无显著差异（分别为1.13±0.13 vs. 1.07±0.17 μmol·min⁻¹·g⁻¹）。相比之下，慢性代谢性酸中毒大鼠的肾脏产生的NH₃明显多于这两组（2.73±0.29 μmol·min⁻¹·g⁻¹）。与对照组相比，慢性呼吸性酸中毒大鼠的皮质肾小管在NH₃（分别为8.8±0.8 vs. 11.6±0.8 μmol·min⁻¹·g⁻¹）和葡萄糖（分别为1.38±0.08 vs. 1.41±0.13 μmol·min⁻¹·g⁻¹）产生方面也没有适应的迹象，而慢性代谢性酸中毒使氨生成和糖异生增加了两倍或更多。因此，全身低pH值并不能解释肾脏产生氨或葡萄糖能力的适应性变化。（摘要截取自250字）
