INFLUENCE OF SODIUM NITROPRUSSIDE AS A DONOR OF NITRIC OXIDE ON ATPASE ACTIVITY OF RAT LIVER MITOCHONDRIA

SHKODROVA, M., M. CHICHOVA, D. GANCHEV, I. SAZDOVA and I. MINKOV, 2013. Infl uence of sodium nitroprusside as a donor of nitric oxide on ATPase activity of rat liver mitochondria. Bulg. J. Agric. Sci., Supplement 2, 19: 167–170 Nitric oxide (NO) is a signal molecule, which is unstable in aqueous solution and rapidly converts to peroxynitrite and nitrate. Regardless of the strong evidences that NO and its derivatives inhibit the mitochondrial function as a result of interactions with most of the respiratory chain transporters, the data concerning the overall process of the oxidative phosphorylation are contradictory. The present work was undertaken to study the infl uence of sodium nitroprusside (SNP) as a donor of NO on ATPase activity of rat liver mitochondria. ATPase activity was determined by measurement of inorganic phosphate increase in the reaction medium. The results obtained when SNP was added directly to the reaction medium were rather contradictory. We observed an inhibition of the ATPase activity of rat liver mitochondria uncoupled by freezing/thawing, whereas preliminary deactivation of the compound provoked the opposite effect. SNP added directly to the reaction medium led to an increase of the ATPase activity of submitochondrial particles (SMP). These effects may be result from the infl uence of NO itself, donor molecule, products of its degradation and/or from their combined effect. Therefore, a specially constructed experimental system allowing separation of NO from the molecule of its donor was used. In these experiments, a thin polytetrafl uoroethylene membrane separated the cuvette where SNP was added from that where ATPase reaction was performed. Thus, solutions were isolated, but NO was freely diffusing. Using this system we found an inhibition of ATPase activities of rat liver uncoupled mitochondria and of SMP. This effect was abolished after preliminary deactivation of SNP. We concluded that the ATPase activity changes were due to the infl uence of NO diffusing through the membrane. The present experimental system can be applicable to study different biological samples sensitive to NO.