3,3¢-Dipropyl-2,2¢-thiadicarbocyanine iodide [DiS-C3 (5)], often used as a tracer dye to assess the mitochondrial mem-brane potential, was investigated in detail regarding its effects on the structure and function of isolated mitochon-dria. As reported previously, DiS-C3(5) had an inhibitory effect on NADH-driven mitochondrial electron transfer. On the contrary, in the presence of inorganic phosphate, DiS-C3(5) showed dose-dependent biphasic effects on mito-chondria energized by succinate. At higher concentrations, such as 50lM,DiS-C3(5) acceleratedmitochondrial oxygen consumption. .
