Tabuchi Y, Takeguchi M, Asano S, Takeguchi N
Faculty of Pharmaceutical Sciences, Toyama Medical and Pharmaceutical University, Japan.
Jpn J Physiol. 1992;42(4):577-89. doi: 10.2170/jjphysiol.42.577.
A membrane fraction from rat distal colon contained both ouabain-sensitive and -insensitive K(+)-ATPase activities, which were measured under Na(+)-free conditions. About 38% of the ouabain-insensitive K(+)-ATPase activity was inhibited by vanadate. It was determined whether the ouabain-insensitive, vanadate-sensitive K(+)-ATPase in the colon is similar or identical to gastric H+,K(+)-ATPase. This colonic K(+)-ATPase activity was inhibited completely by monoclonal antibody HK4001, which inhibits the hog gastric H+,K(+)-ATPase activity but not Na+,K(+)-ATPase or Ca(2+)-ATPase. The colonic ATPase activity was inhibited partly by SCH 28080, which is a specific reversible inhibitor of gastric H+,K(+)-ATPase. The colonic ATPase activity was stimulated by low concentrations of K+ (its half-maximal stimulating concentration was 1 mM) and inhibited by high concentrations of K+ (its half-maximal inhibiting concentration was 10 mM), indicating that high and low K+ affinity sites are present in the colonic enzyme as in gastric H+,K(+)-ATPase and that this enzyme is not fully operative under normal physiological conditions. Two other monoclonal antibodies, which inhibit the gastric H+,K(+)-ATPase activity, did not inhibit the colonic K(+)-ATPase activity. The present results suggest that the colonic ouabain-insensitive K(+)-ATPase is partly similar but not identical to the gastric H+,K(+)-ATPase.
大鼠远端结肠的膜组分含有哇巴因敏感和不敏感的K(+) - ATP酶活性，这些活性是在无钠条件下测量的。约38%的哇巴因不敏感K(+) - ATP酶活性被钒酸盐抑制。研究了结肠中哇巴因不敏感、钒酸盐敏感的K(+) - ATP酶是否与胃H+，K(+) - ATP酶相似或相同。这种结肠K(+) - ATP酶活性被单克隆抗体HK4001完全抑制，HK4001抑制猪胃H+，K(+) - ATP酶活性，但不抑制Na+，K(+) - ATP酶或Ca(2+) - ATP酶。结肠ATP酶活性被SCH 28080部分抑制，SCH 28080是胃H+，K(+) - ATP酶的特异性可逆抑制剂。结肠ATP酶活性受到低浓度K+的刺激（其半最大刺激浓度为1 mM），并受到高浓度K+的抑制（其半最大抑制浓度为10 mM），这表明结肠酶中存在高亲和力和低亲和力的K+位点，就像胃H+，K(+) - ATP酶一样，并且这种酶在正常生理条件下并未完全发挥作用。另外两种抑制胃H+，K(+) - ATP酶活性的单克隆抗体并未抑制结肠K(+) - ATP酶活性。目前的结果表明，结肠中哇巴因不敏感的K(+) - ATP酶部分类似于但并不等同于胃H+，K(+) - ATP酶。
