[Investigation of Ca2+ -induced changes of membrane potential of smooth muscle mitochondria using flow cytometric...

Using flow cytometric analysis and potential-sensitive fluorescent dye TMRM Ca2+ -induced changes of membrane potential of isolated smooth muscle mitochondria were studied. It was shown, that Ca2+ (100 microM) addition to the incubation medium induced mitochondrial membrane depolarization that probably could be explained by Ca2+/H+ -exchanger activation which functioning lead to membrane potential dissipation. In the case of ruthenium red (10 microM) preliminary presence in incubation medium, Ca2+ (100 microM) addition did not lead to membrane potential dissipation. Hence, membrane potential dissipation was caused by an increase of matrix Ca2+ concentration. In the presence of Mg2+ (3 mM) and ATP (3 mM), Ca2+ addition did not cause depolarization. It was supposed that in this case ATP synthase acted in the opposite direction as H+ -pump and prevented from mitochondrial membrane potential dissipation. Thus, the flow cytometry method allows to register membrane potential of isolated smooth muscle mitochondria and also to test the effectors, capable to modulate this parameter.