Bengele H H, McNamara E R, Schwartz J H, Alexander E A
Thorndike Memorial Laboratory, Boston City Hospital, Massachusetts.
Am J Physiol. 1988 Dec;255(6 Pt 2):F1155-9. doi: 10.1152/ajprenal.1988.255.6.F1155.
Chronic acid feeding (ACD) stimulates and chronic alkali (AKL) feeding suppresses acid secretion along the inner medullary collecting duct (IMCD) of the rat. The purpose of these experiments was to determine whether these stimuli produce IMCD acidification adaptation. We tested this hypothesis by acutely changing systemic PCO2 in rats chronically fed ACD or ALK. Microcatheterization was used to measure pH and PCO2 and samples were simultaneously obtained for measurement of bicarbonate, titratable acid (TA), and ammonium. In 10 ACD rats (arterial pH, 7.26 +/- 0.01; PCO2, 88 +/- 1 mmHg) acid secretion along the IMCD was 506 +/- 88 nmol/min. In 10 ALK rats with similar arterial gases (pH, 7.16 +/- 0.02; PCO2, 82 +/- 1 mmHg) IMCD acid secretion was only 284 +/- 57 nmol/min, P less than 0.05. In ACD rats made hypocarbic (pH, 7.26 +/- 0.03; PCO2, 24 +/- 1 mmHg), IMCD acid secretion was 163 +/- 55 nmol/min. These data were compared with previously studied rats eating a regular diet. Acute hypocarbia (pH, 7.54 +/- 0.02; PCO2, 20 +/- 1 mmHg) completely suppressed acid secretion, 4 +/- 23 nmol/min, along the IMCD. We conclude that chronic alterations in acid-base status provide an IMCD "set" where comparable stimuli produce significant differences in IMCD acidification. These data provide additional support for the concept of IMCD acidification adaptation.
长期给予酸（ACD）可刺激大鼠髓质内集合管（IMCD）的酸分泌，而长期给予碱（AKL）则抑制该部位的酸分泌。这些实验的目的是确定这些刺激是否会导致IMCD酸化适应。我们通过急性改变长期给予ACD或ALK的大鼠的全身PCO₂来检验这一假设。采用微导管插入术测量pH和PCO₂，并同时采集样本以测定碳酸氢盐、可滴定酸（TA）和铵。在10只给予ACD的大鼠中（动脉pH值为7.26±0.01；PCO₂为88±1 mmHg），沿IMCD的酸分泌为506±88 nmol/分钟。在10只动脉血气类似的给予ALK的大鼠中（pH值为7.16±0.02；PCO₂为82±1 mmHg），IMCD酸分泌仅为284±57 nmol/分钟，P<0.05。在给予ACD的大鼠中使其处于低碳酸血症状态（pH值为7.26±0.03；PCO₂为24±1 mmHg），IMCD酸分泌为163±55 nmol/分钟。这些数据与之前研究的正常饮食大鼠的数据进行了比较。急性低碳酸血症（pH值为7.54±0.02；PCO₂为20±1 mmHg）完全抑制了沿IMCD的酸分泌，为4±23 nmol/分钟。我们得出结论，酸碱状态的慢性改变为IMCD提供了一种“设定”，在这种设定下，类似的刺激会导致IMCD酸化产生显著差异。这些数据为IMCD酸化适应的概念提供了额外的支持。
