A quantitative correlation between the kinetics of solutes and water translocation in Liver Mitochondria

Abstract

A procedure is described for the calculation of solute fluxes in mitochondria from absorbance measurements. The procedure assumes that mitochondria behave as osmometers and that they are always at osmotic equilibrium. The rates and amounts of K⁺ translocation have been calculated simultaneously, with the photometric procedure and electrometrically, during passive, K⁺ efflux coupled to Ca⁺⁺ uptake and during active K⁺ uptake and passive K⁺ release coupled with anion translocation. Good agreement has been found between the two sets of measurements. The data are compatible with the concept that the energy-linked, ion translocation-coupled, mitochondrial swelling is osmotic in nature. It is concluded that the changes of absorbance are quantitatively related to changes in the inner volume and therefore the photometric procedure can be used to calculate, ion fluxes of osmotically active species under various circumstances.