THE RESPIRATORY DEPENDENT SWELLING OF LIVER MITOCHONDRIA

Abstract

The respiratory dependent swelling of isolated rat liver mitochondria was studied in sucrose and in potassium chloride media.In a sucrose medium it was found that mitochondria did not swell in the absence of respiration over the pH range 7.0–8.0. However, swelling of mitochondria readily occurred during the oxidation of endogenous or added respiratory substrates. Maximum rates of swelling at pH 7.0 were observed with ascorbate, reduced glutathione, and reduced nicotinamide–adenine dinucleotide (NADH). The swelling induced by substrate oxidation in a sucrose medium was markedly inhibited by the addition of KCl.In a KCl medium, mitochondria swelled in the absence of respiration at acid (6.0) and at alkaline (8.0) pH values, but were stable at pH 7.0–7.4. Endogenous respiration did not modify these results. The addition of β-hydroxybutyrate induced maximum swelling at pH 7.0. The extent of swelling produced by this substrate diminished when either the pH or the molarity of the buffer was increased. Ascorbate and reduced glutathione failed to induce swelling in a KCl medium. NADH in a KCl medium produced swelling to about the same extent as that in a sucrose medium. However, the onset of the swelling was delayed in the KCl medium. This lag period was shortened by the addition of rotenone and it was lengthened when either the molarity or the pH of the buffer was increased.An attempt has been made to relate these results to proton pressure produced in the mitochondrial membranes during electron transport.