Watanabe T, Suzuki T, Suzuki Y
Department of Physiology, Yamagata University School of Medicine, Japan.
Am J Physiol. 1990 Apr;258(4 Pt 1):G506-11. doi: 10.1152/ajpgi.1990.258.4.G506.
We have previously shown that an ouabain-sensitive H(+)-K+ exchange mechanism may be present in the apical membrane of guinea pig distal colon [Y. Suzuki and K. Kaneko. Am. J. Physiol. 256 (Gastrointest. Liver Physiol. 19): G979-G988, 1989]. The present study is aimed to demonstrate the presence of an ATPase responsible for this exchange. ATPase activity was determined in the crude membrane fraction of the colonic epithelial cell homogenate. ATPase activity under Na(+)-free conditions was increased by the addition of K+, with a half-maximal effect at 55 microM. This increase was completely abolished by 1 mM ouabain, suggesting the presence of an ouabain-sensitive K(+)-ATPase. The ouabain-sensitive K(+)-ATPase activity was inhibited by vanadate (100 microM) and N,N'-dicyclohexylcarbodiimide (100 microM) but was resistant to oligomycin (4.5 micrograms/ml) and NaN3 (1 mM). The ouabain-sensitive K(+)-ATPase activity was observed in the distal but not in the proximal colon, whereas Na(+)-K(+)-ATPase activity was distributed along the entire colon. Omeprazole (40 microM) reduced the colonic K(+)-ATPase activity by 31 +/- 6%, whereas it reduced the gastric K(+)-ATPase activity by 78 +/- 8%. These results suggest that the ouabain-sensitive K(+)-ATPase as demonstrated here is responsible for the colonic H(+)-K+ exchange. This ATPase could be similar to but is not identical with either Na(+)-K(+)-ATPase or gastric H(+)-K(+)-ATPase.
我们之前已经表明，哇巴因敏感的H(+)-K+交换机制可能存在于豚鼠远端结肠的顶端膜中[Y. 铃木和金子健。《美国生理学杂志》256 (胃肠肝脏生理学19): G979 - G988, 1989]。本研究旨在证明负责这种交换的ATP酶的存在。在结肠上皮细胞匀浆的粗膜部分测定了ATP酶活性。在无Na(+)条件下，加入K+可增加ATP酶活性，在55 microM时达到最大效应的一半。1 mM哇巴因可完全消除这种增加，提示存在哇巴因敏感的K(+)-ATP酶。哇巴因敏感的K(+)-ATP酶活性受到钒酸盐(100 microM)和N,N'-二环己基碳二亚胺(100 microM)的抑制，但对寡霉素(4.5微克/毫升)和NaN3(1 mM)有抗性。在远端结肠观察到哇巴因敏感的K(+)-ATP酶活性，而近端结肠未观察到，而Na(+)-K(+)-ATP酶活性沿整个结肠分布。奥美拉唑(40 microM)使结肠K(+)-ATP酶活性降低31±6%，而使胃K(+)-ATP酶活性降低78±8%。这些结果表明这里所证明的哇巴因敏感的K(+)-ATP酶负责结肠的H(+)-K+交换。这种ATP酶可能与Na(+)-K(+)-ATP酶或胃H(+)-K(+)-ATP酶相似但不相同。
