[Study of sarcoplasmic reticulum membrane permeability using potential-sensitive fluorescent probes]

A new method is proposed for quantitative studies of SR membrane permeability. It involves measuring to diffusion potentials, arising at salt concentration gradient on the SR membrane due to its anion and cation permeability differences. Visualization of processes of negative chloride potential arising in adding MeCl2 and its further dissipation was realized with diS-C3-(5). A/23187 and X-537A in small concentrations reduce the amplitude and the length of fluorescent signal, while in strong concentrations they fully prevent it. Dissipation kinetics of chloride potential caused by the SR membrane permeability for Me2+ is used for quantitative analysis of this permeability. It is shown that the parameter tau 1/2 corresponds to the moment of time when the inside concentration of Me2+ becomes equal to the geometric average of the initial concentrations of this ion. The relationship between tau 1/2 and the concentrations of the added MeCl2 and the penetration ion (K+) and temperature were studied. It was shown that the membrane permeability gain with increasing MeCl2 concentration is due to accelerating action of the membrane potential. A laser two-wave, two-beam installation was described which allows to study SR membrane permeability with potential-sensitive probe fluorescence and light scattering on the same sample. Correlation between the signals obtained simultaneously with these independent methods was shown.