Personal review RELATIONSHIP BETWEEN MEMBRANE POTENTIAL, CALCIUM FLUXES AND MATRIX SWELLING IN RAT LIVER MITOCHONDRIA; EFFECT OF ETHANOL FEEDING

The main objective of the present work was to establish the exact temporal relationship between membrane potential collapse, calcium release and mitochondrial matrix swelling during a metabolic stress. For this purpose, liver mitochondria were prepared from normal and ethanol-fed rats and incubated in different media placed in the the cuvettes of a diode array spectrophotometer, with succinate as substrate. The media used were supplemented with an appropriate probe for either membrane potential or calcium fluxes and matrix swelling was monitored in parallel with each of the two parameters. A series of discrete CaCl2 pulses were used to alter the three respirationdependent parameters and to establish the mitochondrial sensitivity to metabolic stress. From the comparison of the spectrophotometric recordings, a correlation could be established between the type of medium used and/or the concentration of calcium added to the mitochondrial suspension and the moments of initiation of swelling, ∆Ψ collapse and calcium release (occurring in this order). Significant differences in this regard were also noticed between the mitochondria of the control and of the ethanol-fed rats. Based on the present results, certain situations reported in the literature, in which membrane potential is apparently preserved after the occurrence of the mitochondrial permeability transition, could be explained if the mechanisms of response of the most frequently used membrane potential sensitive dyes were seriously taken into consideration.