CHANGE IN SURFACE CHARGE OF MITOCHONDRIAL INNER MEMBRANE UPON ENERGIZATION
能量化时线粒体内膜表面电荷的变化

The binding of fluorescence probe ANS to rat liver mitochondrial inner membrane (mitoplasts) and the electrophoretic mobility of mitoplasts measureed with electrophoretic laser light scattering technique were investigated to determine the change in surface properties upon energization.Upon energization the fluorescence of ANS bound to mitoplasts altered in either directions depending on the media used. In unbuffered solution (containing 0.225 M mannitol and 0.075 M sucrose pH 7.4), addition of ATP resulted in the increase of ANS fluorescence. The magnitude of fluorescence enhancement depended on the pH of medium and the amount of ATP added. In buffered solution (containing 0.225 M mannitol, 0.075 M sucrose and 2 mM HEPES pH 7.4), energization by ATP (0.25mM - l.0mM) resulted in the decrease of ANS fluorescence. But with the increase of ATP added the fluorescence intensity of ANS changed from decrease to increase gradually. Upon energization the electrophoretic mobility of mitoplasts was always slower than that in nonenergized state, however. The electrophoretic mobility of mitoplasts reduced from 1. 13 × 10-4 cm2/s·v to 0.28 × 10-4cm2/s·v after addition of 0.5 mM ATP in unbuffered solution, and from 8.49 × 10-4cm2/s·v to 1.35 × 10-4cm2/s·v in buffered solution. It was observed that the decrease in electrophoretic mobility of mitopasts was related to the amount of ATP added in both unbuffered and buffered solution.All these results obtained, with one exception that ANS fluorescence was decreased on addition of ATP (0.25mM-lmM) in buffered solution, make the evidence that the surface charge on the cytosolic surface of mitoplasts decrease upon energization by ATP, because of the complex nature of ANS responses to energization in buffered solution it is suggested that both surface potential and transmembrane potential be involved in the alteration of ANS fluorescence upon energization.