Hersey S J, Steiner L, Mendlein J, Rabon E, Sachs G
Department of Physiology, Emory University, Atlanta, GA 30322.
Biochim Biophys Acta. 1988 Aug 31;956(1):49-57. doi: 10.1016/0167-4838(88)90296-8.
The interaction between SCH28080 and omeprazole, two specific inhibitors of gastric H+/K+-ATPase, was investigated using gastric glands and isolated gastric membranes. For gastric glands, inhibition of acid formation by SCH28080 was not reversed by washing whereas inhibition by omeprazole was partially reversed after washing. These features are opposite to what is found with isolated membranes. However, if gastric glands were permeabilized with digitonin after exposure to the inhibitors and recovery measured as ATP-dependent acid formation or H+/K+-ATPase activity, inhibition by SCH28080 was completely reversed while inhibition by omeprazole was non-reversible. Using a procedure of pretreatment with inhibitors followed by permeabilization and assay of recovered activity, it was found that a combined treatment with SCH28080 plus omeprazole prevented the irreversible inhibition by omeprazole, i.e. acid forming capability and ATPase activity were fully recovered. In order to test the possibility that SCH28080 prevented activation of omeprazole by dissipating an acid environment, control experiments were performed with SCN, which gave equivalent dissipation of the acid gradient but did not prevent the irreversible inhibition by omeprazole. These results were confirmed in isolated gastric membranes where residual p-nitrophenylphosphatase activity was assayed following exposure of acid transporting vesicles to omeprazole. Compared to control conditions, omeprazole inhibited 48% of the phosphatase activity whereas simultaneous addition of SCH28080 reduced the inhibition to 14%. The results therefore suggest that SCH28080 selectively blocks irreversible inhibition by omeprazole and thus that these two agents interact at a common region of the luminal aspect of the gastric H+/K+-ATPase.
利用胃腺和分离的胃膜，研究了两种胃H⁺/K⁺-ATP酶特异性抑制剂SCH28080和奥美拉唑之间的相互作用。对于胃腺，SCH28080对酸形成的抑制作用经冲洗后不能逆转，而奥美拉唑引起的抑制作用在冲洗后部分逆转。这些特性与在分离膜上观察到的情况相反。然而，如果在暴露于抑制剂后用洋地黄皂苷使胃腺通透化，并以ATP依赖性酸形成或H⁺/K⁺-ATP酶活性来测定恢复情况，SCH28080引起的抑制作用可完全逆转，而奥美拉唑引起的抑制作用则不可逆。采用先用抑制剂预处理，然后通透化并测定恢复活性的方法，发现SCH28080与奥美拉唑联合处理可防止奥美拉唑的不可逆抑制作用，即酸形成能力和ATP酶活性完全恢复。为了测试SCH28080通过消除酸性环境来阻止奥美拉唑活化的可能性，用硫氰酸盐进行了对照实验，硫氰酸盐能使酸性梯度得到同等程度的消除，但不能阻止奥美拉唑的不可逆抑制作用。在分离的胃膜中也证实了这些结果，在将酸转运小泡暴露于奥美拉唑后，测定了残留的对硝基苯磷酸酶活性。与对照条件相比，奥美拉唑抑制了48%的磷酸酶活性，而同时加入SCH28080可将抑制作用降低至14%。因此，结果表明SCH28080选择性地阻断了奥美拉唑的不可逆抑制作用，从而提示这两种药物在胃H⁺/K⁺-ATP酶腔面的一个共同区域相互作用。
