大鼠远端结肠的HCO3-分泌：抑制剂和细胞外Na+的作用

HCO3- secretion by rat distal colon: effects of inhibitors and extracellular Na+.

作者信息

Feldman G M

机构信息

Department of Medicine, McGuire Veterans Affairs Medical Center, Richmond, Virginia.

出版信息

Gastroenterology. 1994 Aug;107(2):329-38. doi: 10.1016/0016-5085(94)90156-2.

DOI:10.1016/0016-5085(94)90156-2

PMID:8039609

Abstract

BACKGROUND/AIMS: The large intestine secretes HCO3- via a Cl-/HCO3- exchange mechanism located in the apical membrane of colonocytes. However, an additional transport system(s) must facilitate HCO3- (OH-) entry or H+ exit across the basolateral cell surface. The aim of this study was to determine that mechanism(s).

METHODS

A modified Ussing apparatus was used to measure net HCO3- secretion in segments of rat distal colon.

RESULTS

When added to the serosal solution, 10 mmol/L 4-acetamido-4'-isothiocyano-2,2'-disulfonic acid stilbene (SITS), 1 mmol/L SITS and 0.1 mmol/L diisothiocyanostilbene-2,2'-disulfonic acid, inhibited HCO3- secretion by 88%, 51%, and 30%, respectively. However, the Na+/H+ exchange inhibitors, amiloride (1 mmol/L), dimethylamiloride (0.1 mmol/L), ethylisopropylamiloride (0.1 mmol/L), failed to affect HCO3- secretion. Acetazolamide (1 mmol/L) blocked HCO3- secretion by approximately 60% when in the serosal solution but had little effect when in the mucosal solution. Ion substitution studies showed that HCO3- secretion required Na+ in the serosal solution (K0.5 approximately 12 mmol/L). HCO3- secretion was unaffected by depolarizing the basolateral membrane potential with K(+)-rich medium.

CONCLUSIONS

These data are consistent with Na+ linked HCO3- transport across the colonocyte basolateral membrane, which appears to be electroneutral.

摘要

背景/目的：大肠通过位于结肠上皮细胞顶端膜的Cl⁻/HCO₃⁻交换机制分泌HCO₃⁻。然而，必须有其他转运系统促进HCO₃⁻（OH⁻）进入或H⁺穿过基底外侧细胞表面排出。本研究的目的是确定该机制。

方法

使用改良的Ussing装置测量大鼠远端结肠段的净HCO₃⁻分泌。

结果

当加入浆膜溶液时，10 mmol/L 4-乙酰氨基-4'-异硫氰基-2,2'-二磺酸芪（SITS）、1 mmol/L SITS和0.1 mmol/L二异硫氰基芪-2,2'-二磺酸分别抑制HCO₃⁻分泌88%、51%和30%。然而，Na⁺/H⁺交换抑制剂阿米洛利（1 mmol/L）、二甲基阿米洛利（0.1 mmol/L）、乙基异丙基阿米洛利（0.1 mmol/L）对HCO₃⁻分泌无影响。乙酰唑胺（1 mmol/L）在浆膜溶液中时可阻断约60%的HCO₃⁻分泌，但在粘膜溶液中时影响很小。离子替代研究表明，HCO₃⁻分泌需要浆膜溶液中有Na⁺（K0.5约为12 mmol/L）。用富含K⁺的培养基使基底外侧膜电位去极化对HCO₃⁻分泌无影响。