Figure 2.

Effect of ML 3000 acidification on H,K-ATPase activity (A), and ML 3000 inhibition of H,K-ATPase activity is reversible (B). (A) ML 3000 aliquots (10 mM in 5 mM Tris-HCl) were titrated to pHs ranging from 2.0 to 7.4 for 30 min before addition to standard ATPase assay buffer (pH 7.4) containing gastric microsomes. (B) Gastric microsomes were treated with a maximally-inhibitory concentration (100 μM) of ML 3000. The microsomal suspension was then diluted with a large excess of buffer to reduce the ML 3000 concentration from 100 μM to 3.3 μM. In both (A) and (B), the data-points show mean ± s.e. from three independent assays in each of which SCH28080-sensitive ATPase activity was measured in triplicate.