Studies on the Mechanism of Swelling, Lysis, and Distintegration of Isolated Liver Mitochondria Exposed to Mixtures of Qxidized and Reduced Glutathione*

Lehninger and Schneider (1) studied the swelling of isolat,ed liver mitochondria induced by reduced glutathione (GSH). One outstanding difference from thyroxine-induced swelling was that GSH-induced swelling was not reversible. These studies have been extended by Lehninger and Gotterer (2, 3) with the discovery that GSH-induced swelling is reversed by adenosine triphosphate + Mg ++ + bovine serum albumin if a specific protein, C factor, is added. Recently Seubert, Wojtczak, and Lehninger (4) identified this protein as being a mixture of GSH peroxidase and catalase. Neubert and Lehninger (5-7) have also reported that oxidized glutathione (GSSG) has a marked stimulating effect on the rate of swelling with GSH. In fact, swelling wit,h GSH may not occur at all if there is no GSSG present. In our own work with GSH (8), the extremely low 0~~0 readings reached led us to suspect that GSH-induced swelling was more closely related to ascorbate-induced lysis (9, 10) than to phosphate + substrate-induced swelling. Resolution of the question concerning the degree to which GSH-induced swelling is related to (a) substrate and electron transport-dependent swelling, (b) specific changes induced through membrane thiol and disulfide groups, or (c) lipid peroxide formation leading to swelling, lysis, and disintegration is very important. The mechanism of action of glutathione on mitochondrial membranes is of special interest because of evidence suggesting that disulfide interchange reactions in membrane structures may control permeability (11, 12). This paper reports investigations on GSHand GSSG + GSH-induced swelling. In earlier work, GSH-induced swelling usually reduced the 0~~ o f dilute suspensions to values considerably below those reached with phosphate + P-hydroxybutyrat,e, but such was not always the case when as high as 20 rnnl GSH was used. Our initial working hypothesis was that a substrat,e role for GSH might be manifest at very high concentrations because the lytic effect of lower concentrations was sup-