INTERDEPENDENCE BETWEEN MITOCHONDRIAL MATRIX VOLUME AND THE EXTRA-MITOCHONDRIAL RATIO OF [ATP]-[ADP] [INORGANIC-PHOSPHATE]

ATP or ATP combined with EDTA or EGTA [ethylene glycoltetraacetic acid] can act as a chelator to catalyze succinate-driven, Pi-requiring expansion of [rat liver] mitochondrial inner membrane-matrices. Contraction of these swollen mitochondria can be induced with antimycin, MgCl2 and ADP. The magnitude of ADP-induced contractions of mitochondria, swollen in the presence of ATP, is dependent on [ADP] and may be altered by the extramitochondrial concentrations of Pi and ATP. The extent of contraction (+.DELTA.A520 [change in absorbance at 520 nm]) is a linear function of the thermodynamic parameter, -.DELTA. Gp (free energy of ATP hydrolysis), provided excessive concentrations of reactants are not present and the extents of matrix swelling are similar (e.g., .DELTA.A520 is about 0.250) before starting contraction with ADP.