The Effect Of NO Donor on Calcium Uptake and Reactive Nitrogen Species Production in Mitochondria.

BACKGROUND/AIMS NO and reactive nitrogen species (RNS) are thought to be physiologically important effectors of mitochondrial calcium transport, but this issue was not studied in a living organism. According to literature, the modulation of Ca2+ uptake could influence RNS production via the action on mitochondrial NO synthase (mtNOS). The aim of this work was to study the effect of in vivo administration of NO donor nitroglycerine (NG) on matrix Ca2+ accumulation, RNS production and mtNOS activity. METHODS Ca2+ uptake was studied spectrophotometrically with arsenazo-III. The amounts of stable RNS (nitrite, nitrate and nitrosothiols) and L-citrulline, the product of enzymatic NOS activity, were determined analytically. RESULTS NG administration resulted in dose-dependent short-term increase in Ca2+-uptake accompanied by essential rise in L-citrulline and RNS content in mitochondria. In parallel, dose-dependent elevation of hydroperoxide production was detected. Ca2+-uniporter activity was not affected, but mitochondrial permeability transition pore (MPTP) was effectively blocked by NO. CONCLUSION Our results indicate that MPTP blockage by NO was the primary cause for the increase in calcium uptake which eventually resulted in the activation of mtNOS and RNS production. Improved Ca2+ accumulation in mitochondria, together with MPTP blockage, may contribute to well-known cardioprotective effects of pharmacological donors of nitric oxide.