[Free energy of the accumulation of a fluorescent cation probe within lymphocyte mitochondria]

Fluorescent probe-cation 4-(p-dimethylaminostyryl)-1-methylpyridinium (DSM) can be accumulated in mitochondria of rat thymus lymphocytes. A method is proposed for microfluorometric measuring of DSM concentrations ratio inside the thymocyte mitochondria and in the external medium. This method requires no knowledge about the cell and mitochondria volume, the number of accumulated probe and formation of ionic gradients in the cell by carriers. DSM concentration in energisized mitochondria of the thymocyte exceeds its concentration in the external medium by 10(4) times. This corresponds to the free energy accumulated by DSM equaling 5.2 +/- 0.2 kcal/mole. If such work on the probe accumulation is performed by the electrostatic fields on the plasma and mitochondrial cell membranes, the sum of the potentials of these two fields is 230 +/- 10 mV.