McKinney T D, Davidson K K
Department of Medicine, University of Texas Health Science Center, San Antonio.
Am J Physiol. 1987 Nov;253(5 Pt 2):F816-22. doi: 10.1152/ajprenal.1987.253.5.F816.
The purpose of this study is to characterize the features of bicarbonate (total CO2) transport in isolated perfused collecting tubules obtained from the outer stripe of the outer medulla (OMCTos) of rabbit kidneys. Under control conditions (25 mM HCO3- in the perfusate and bath), all OMCTos studied absorbed total CO2 at a mean rate of 8.61 +/- 0.44 pmol.mm-1.min-1. Ouabain (10(-4) M in the bath) did not affect the rate of total CO2 absorption (JtCO2). Addition of the diethylstilbene 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) in a concentration of 10(-4) M or replacement of bath chloride by gluconate reduced JtCO2 by approximately 50%, whereas replacement of luminal chloride increased JtCO2 by 40%. The carbonic anhydrase inhibitors acetazolamide and ethoxyzolamide in concentrations of 10(-4) M had little effect on JtCO2. In a concentration of 10(-3) M, acetazolamide reduced JtCO2 by only 31%. OMCTos obtained from rabbits with ammonium chloride-induced metabolic acidosis did not have increased rates of total CO2 absorption compared with the control, but treatment of animals with mineralocorticoids increased JtCO2. These results indicate that OMCTos are capable of significant bicarbonate absorption in vitro. This absorption 1) is independent of sodium transport, 2) appears to require, at least in large part, HCO3- or OH- -Cl- exchange across the basolateral cell membrane of acid-secreting cells, 3) is much more resistant to inhibition by carbonic anhydrase inhibitors than reported previously for other rabbit nephron segments, and 4) is stimulated by prior mineralocorticoid treatment of animals but not by prior metabolic acidosis in vivo.
本研究的目的是描述从兔肾外髓质外层条纹（OMCTos）分离得到的灌注集合小管中碳酸氢盐（总二氧化碳）转运的特征。在对照条件下（灌注液和浴液中碳酸氢盐浓度为25 mM），所有研究的OMCTos以平均速率8.61±0.44 pmol·mm⁻¹·min⁻¹吸收总二氧化碳。哇巴因（浴液中浓度为10⁻⁴ M）不影响总二氧化碳吸收速率（JtCO₂）。加入浓度为10⁻⁴ M的二乙基stilbene 4,4'-二异硫氰酸酯基stilbene-2,2'-二磺酸（DIDS）或用葡萄糖酸盐替代浴液中的氯离子可使JtCO₂降低约50%，而用葡萄糖酸盐替代管腔中的氯离子可使JtCO₂增加40%。浓度为10⁻⁴ M的碳酸酐酶抑制剂乙酰唑胺和乙氧唑胺对JtCO₂影响很小。浓度为10⁻³ M时，乙酰唑胺仅使JtCO₂降低31%。与对照组相比，氯化铵诱导代谢性酸中毒的兔的OMCTos的总二氧化碳吸收速率没有增加，但用盐皮质激素治疗动物可增加JtCO₂。这些结果表明，OMCTos在体外能够显著吸收碳酸氢盐。这种吸收1）独立于钠转运，2）似乎至少在很大程度上需要在分泌酸细胞的基底外侧细胞膜上进行HCO₃⁻或OH⁻ - Cl⁻交换，3）比先前报道的其他兔肾单位节段对碳酸酐酶抑制剂的抑制作用更具抗性，4）受动物先前的盐皮质激素治疗刺激，但不受体内先前的代谢性酸中毒刺激。
