Welbourne T C, Cronin M J
Department of Physiology, Louisiana State University Medical Center, Shreveport 71130.
Am J Physiol. 1991 Jun;260(6 Pt 2):R1036-42. doi: 10.1152/ajpregu.1991.260.6.R1036.
The effect of growth hormone on tubular H+ secretion by the hypophysectomized and intact rat was studied in the isolated functioning kidney. Net acid secretion was estimated as the sum of HCO3- absorption plus NH+4 excretion. Kidneys from either intact or hypophysectomized rats were isolated and perfused over a 90-min time course during which either recombinant human growth hormone (GH), insulin-like growth factor-1 (IGF-1), porcine insulin, or vehicle was added; hormone response was then compared with the time controls. Compared with kidneys from intact rats, hypophysectomized rat kidneys exhibited a marked acidification defect, net H+ secretion, 13,530 +/- 600 vs. 17,860 +/- 810 (SE) nmol/ml of glomerular filtrate (GF). Administering GH (50 nM) increased net H+ secretion within 15 min in both hypophysectomized and intact groups to a maximum of 17,950 +/- 910 and 20,960 +/- 1,100 nmol/ml GF, respectively; neither insulin nor IGF-1 (50 nM) was able to mimic GH's effect. Addition of 1 mM amiloride completely abolished the GH-accelerated acid secretion and greater than 70% of the basal net acid secretion rate. Furthermore, GH-enhanced volume absorption was also abolished by amiloride, although neither NaCl nor glutamine absorption was affected. GH-accelerated acid secretion and coupled volume absorption could be observed at concentrations as low as 3.5 nM with half-maximal effect at 12 nM, which is within the range of GH concentration achieved during episodic GH surges. Finally administering GH in vivo to hypophysectomized rats enhanced net acid secretion and urinary acidification, consistent with accelerated tubular H+ secretion as one physiological expression of GH action.
在离体的有功能的肾脏中，研究了生长激素对垂体切除大鼠和完整大鼠肾小管H⁺分泌的影响。净酸分泌通过HCO₃⁻吸收与NH₄⁺排泄之和来估算。分离完整或垂体切除大鼠的肾脏，并在90分钟的时间过程中进行灌注，在此期间添加重组人生长激素（GH）、胰岛素样生长因子-1（IGF-1）、猪胰岛素或赋形剂；然后将激素反应与时间对照组进行比较。与完整大鼠的肾脏相比，垂体切除大鼠的肾脏表现出明显的酸化缺陷，净H⁺分泌分别为13,530±600与17,860±810（SE）nmol/ml肾小球滤液（GF）。给予GH（50 nM）在15分钟内使垂体切除组和完整组的净H⁺分泌均增加，最高分别达到17,950±910和20,960±1,100 nmol/ml GF；胰岛素和IGF-1（50 nM）均无法模拟GH的作用。添加1 mM氨氯吡脒完全消除了GH加速的酸分泌以及超过70%的基础净酸分泌率。此外，氨氯吡脒也消除了GH增强的容积吸收，尽管NaCl和谷氨酰胺的吸收未受影响。在低至3.5 nM的浓度下即可观察到GH加速的酸分泌和相关的容积吸收，在12 nM时达到最大效应的一半，这处于GH脉冲式分泌期间所达到的GH浓度范围内。最后，对垂体切除大鼠进行体内给予GH可增强净酸分泌和尿液酸化，这与肾小管H⁺分泌加速作为GH作用的一种生理表现一致。
