Net H+ and K+ fluxes across the apical surface of rat distal colon

被引:8
作者
Feldman, GM [1 ]
Ickes, JW [1 ]
机构
[1] VIRGINIA COMMONWEALTH UNIV, MED COLL VIRGINIA, MCGUIRE DEPT VET AFFAIRS MED CTR, DEPT PHYSIOL, RICHMOND, VA 23249 USA
来源
AMERICAN JOURNAL OF PHYSIOLOGY-GASTROINTESTINAL AND LIVER PHYSIOLOGY | 1997年 / 272卷 / 01期
关键词
colonic hydrogen-potassium-adenosinetriphosphatase; hydrogen secretion; potassium absorption; potassium transport; potassium-adenosinetriphosphatase; acid-base transport; aldosterone; hyperaldosteronism; carbon dioxide; pH;
D O I
10.1152/ajpgi.1997.272.1.G54
中图分类号
R57 [消化系及腹部疾病];
学科分类号
摘要
The distal colon absorbs K+ (J(K)) and secretes H+ (J(H)) by what is thought to be an H+-K+-adenosinetriphosphatase (H+-K+-ATPase). However the colonic ATPase differs structurally and functionally from the gastric H+-K+-ATPase. To evaluate the link between J(H) and J(K), J(H) and J(K) were simultaneously measured with ion-specific electrodes in segments of rat distal colon. J(H) and J(K) averaged 0.40 +/- 0.03 and 0.30 +/- 0.03 mu eq . h(-1). cm(-2) (n = 191), but J(H) and J(K) did not correlate (r = 0.005, not significant). The gastric H+-K+ pump inhibitors SCK-28080 (100 mu M) and omeprazole (100 mu M): as well as a vacuolar H+-ATPase inhibitor, bafilomycin A(1) (10 mu M), did not affect J(H) or J(K). However, the Na+-K+-ATPase inhibitors ouabain (1 mM) and N-ethylmaleimide (10 mu M) inhibited J(K) but not J(H). Although 1 mM orthovanadate inhibited both J(H) and J(K), at lower concentrations orthovanadate only affected J(K). Furthermore, removing K+ from the medium did not affect J(H) Secondary hyperaldosteronism increased both J(H) and J(K); hu however, ouabain (1 mM) reduced J(K) but not J(H). Cl--free medium inhibited voltage-insensitive J(H) and voltage-sensitive J(K). Medium pH affected J(H), but that effect was contrary to the effect that pH had on Rb+ flux. These data failed to identify a relationship between J(H) and J(K) and appear to suggest that J(H) and J(K) occur by separate pathways.
引用
收藏
页码:G54 / G62
页数:9
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