Novel Application of the Dye, DiS-C3-(3) as a Biosensor of the Renal Membrane Potential Difference

The generation and maintenance of the membrane potential difference is of fundamental importance to the livelihood of every cell. The aim of this study was to show for the first time that the fluorescent indicator, 3'3-dipropylthiacarbocyanine iodide (DiS-C₃-(3)) could be used as a reporter of the membrane potential difference in various membrane vesicle populations isolated from the rat kidney. When these membrane vesicles were added to a solution that imposed different transmembrane potassium gradients the measured change in fluorescence (DF) was dependent upon the predicted membrane potential difference. The more positive the membrane potential difference, the smaller the DF measured. To illustrate the potential applicability of this dye for measuring membrane transport phenomena it was shown that DiS-C₃-(3)fluorescence was sensitive to the more subtle changes in membrane potential evoked by the electrogenic transport activities associated with the H+-coupled uptake of L-glycyl-L-glutamine into brush border membrane vesicles isolated from the rat kidney. These findings demonstrate the suitability of DiS-C₃-(3) as a biosensor of the membrane potential difference with scope for a broad range of applications.