Effect of drug resistance modulator, NO donor, on membrane structure and function of membrane-bound Ca2+-activated Mg2+-dependent ATPase.

Exogenous NO donor 3,3-bis-(nitroxymethyl)oxetane (NMO) was synthesized at the Institute for Problems of Chemical Physics (Russian Academy of Sciences). This compound was shown to inhibit Ca2+-ATPase isolated from normal muscular cells and tumor cells. Both hydrolytic and transport functions of the enzyme were inhibited under these conditions. These changes were probably related to changes in membrane structure caused by NO donor. Our results suggest that changes in intracellular Ca2+ concentration can modulate the formation of tumor drug resistance.