MacLeod R J, Redican F, Lembessis P, Hamilton J R, Field M
Department of Pediatrics, McGill Univeristy-Montreal Children's Hospital Research Institute, Montreal, Quebec, Canada.
Am J Physiol. 1996 Mar;270(3 Pt 1):C786-93. doi: 10.1152/ajpcell.1996.270.3.C786.
Prior studies show that ileal HCO3- secretion is of crypt origin, possibly involving Na+-HCO3- cotransport. To test for the latter, we isolated crypt cells from guinea pig ileum and determined effects of medium HCO3-, Na+, K+, disulfonic stilbenes, and gramicidin on intracellular pH [pHi;2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein fluorescence], cell volume (electronic sizing), and Na+ efflux from 22Na+ -preloaded cells. Ileal crypt cells alkalinized when placed in sodium gluconate-HCO3- medium containing N-5-methyl-5-isobutyl amiloride (1 microM), bumetanide (10 microM) and 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (250 microM which blocks Cl-/HCO3- exchange but not Na+ dependent HCO3- uptake). Depolarization with either gramicidin (50 microM) or 50 mM K+ caused a further 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid (SITS)-inhibitable increase in pHi. Gramicidin also caused SITS-inhibitable cell swelling. Both gramicidin effects were Na+ dependent: at 0 mM Na+, gramicidin acidified and did not alter cell volume; at 25 mM, gramicidin also acidified; at 90 and 140 mM, gramicidin alkalinized and induced cell swelling. HCO3- -dependent SITS-inhibitable Na+ efflux from 22Na+ -preloaded cells was also seen. We conclude that ileal crypt cells engage in electrogenic Na+ -HCO3- symport.
先前的研究表明，回肠HCO3-分泌起源于隐窝，可能涉及Na+-HCO3-共转运。为了验证后者，我们从豚鼠回肠分离出隐窝细胞，并确定培养基中的HCO3-、Na+、K+、二磺酸芪和短杆菌肽对细胞内pH值（pHi；2',7'-双（羧乙基）-5（6）-羧基荧光素荧光）、细胞体积（电子大小测定）以及22Na+预加载细胞的Na+外流的影响。当回肠隐窝细胞置于含有N-5-甲基-5-异丁基阿米洛利（1 microM）、布美他尼（10 microM）和4,4'-二异硫氰酸芪-2,2'-二磺酸（250 microM，可阻断Cl-/HCO3-交换但不影响Na+依赖性HCO3-摄取）的葡萄糖酸钠-HCO3-培养基中时，细胞会碱化。用短杆菌肽（50 microM）或50 mM K+进行去极化会导致pHi进一步出现4-乙酰氨基-4'-异硫氰酸芪-2,2'-二磺酸（SITS）可抑制的升高。短杆菌肽还会导致SITS可抑制的细胞肿胀。短杆菌肽的这两种作用均依赖于Na+：在0 mM Na+时，短杆菌肽使细胞酸化且不改变细胞体积；在25 mM时，短杆菌肽也使细胞酸化；在90和140 mM时，短杆菌肽使细胞碱化并诱导细胞肿胀。还观察到了22Na+预加载细胞中HCO3-依赖性的SITS可抑制的Na+外流。我们得出结论，回肠隐窝细胞参与了电中性的Na+-HCO3-同向转运。
