Influence of omeprasole and lansoprasole on Na+, K+ -ATPase and Mg2+ -ATPase activity of the plasmatic membrane of myometrium smooth muscle cells

The paper deals with the influence of the proton pump inhibitors - omeprasole and lansoprasole on the enzymatic activity of the ouabain-sensitive Na+, K+ -ATPase and the ouabain-resistant Mg2+ - ATPase in the suspension of the myometrium cell plasmatic membranes treated with 0.1% digitonin solution. It was found, that omeprasole and lansoprasole inhibited Na+, K+ -ATPase in the range from 10 to 100 microM. The maximal effect was observed at a concentration of 100 microM with the percentage of inhibition of 81 and 86% at an average as compared with the control for omeprasole and lansoprasole, respectively. The magnitudes of the inhibition coefficient I(0.5) for omeprasole and lansoprasole were 35.60 +/- 0.81 and 29.40 +/- 1.79 microM respectively. Meanwhile cooperative effects on the Na+, K+ - ATPase activity were not found, as the Hill coefficient n(H) for omeprasole was 1.00 +/- 0.08, while for lansoprasole it was 1.20 +/- 0.03. These substances had also insignificant influence on Mg2+ -ATPase: the enzymatic activity was decreased to 84 and 82% as compared with the control with omeprasole and lansoprasole, respectively, in concentration of 100 microM for each inhibitor. The inhibition of Na+, K+ -ATPase activity can evidence for the possible side effects of omeprasole and lansoprasole when they are used for treatment of acid-dependent diseases of the stomach. In addition, obtained experimental data can be useful for further research of the membrane mechanisms of omeprasole and lansoprasole action on cationic exchange in the smooth muscle cells.