[Interaction of diS-C3-(5) and ethylrhodamine with lymphocyte mitochondria]

The interaction of thymocyte mitochondria with two types of dyes - potential indicators commonly used in lymphocyte studies, has been investigated. Ethylrhodamine at concentrations up to 16 microM does not influence the systems of oxidation and energy coupling in lymphocyte mitochondria. Carbocyanines-diS-C3-(5) and diO-C3-(5) inhibit oxygen uptake by the lymphocytes in the presence of glucose and pyruvate at the same low concentrations as does rotenone (40% inhibition occurs at 10 nM). DNP reduces the inhibition of respiration by carbocyanines but not by rotenone. The increase in the fluorescence of diS-C3-(5) and in the rate of oxygen uptake in the absence of diS-C3-(5) occurs at close concentrations of the uncoupler. This indicates that the changes in the fluorescence caused by FCCP reflect the membrane potential of lymphocyte mitochondria. The maintenance of the membrane potential in lymphocyte mitochondria in the presence of diS-C3-(5) provides evidence for the absence of the corresponding changes in mitochondrial ultrastructure after addition of 0.6 microM diS-C3-(5) which completely inhibits oxygen uptake.