Chlorotriethylphosphine gold(I) (TEPAu) is an organo-gold compound that has therapeutic activity in animal models of rheumatoid arthritis. Initial studies have suggested that TEPAu is a potent cytotoxic compound in vitro against a variety of cultured cell types and isolated hepatocytes. Mitochondrial dysfunction induced by this compound has been suggested as a primary biochemical alteration which may result in lethal cell injury in isolated hepatocytes. The purpose of this study was, therefore, to determine the mechanism of TEPAu-induced dysfunction of isolated rat liver mitochondria. TEPAu induced a rapid, concentration-related collapse of the mitochondrial inner membrane potential (EC50 = 24.7 ± 2.5 μm) which was potentiated in Ca2+ loaded mitochondria (EC50 = 11.3 ± 3.8 μm). TEPAu-induced collapse of the membrane potential was partially inhibited in the presence of ruthenium red or EGTA. TEPAu caused the rapid release of mitochondrially sequestered Ca2+ which was not inhibited by ruthenium red and, thus, was not via a reversal of the Ca2+ uniporter. TEPAu caused mitochondrial swelling, increased permeability of the inner membrane, and the oxidation/hydrolysis of endogenous mitochondrial pyridine nucleotides. Addition of exogenous ATP slightly reversed the effects of TEPAu on pyridine nucleotides. TEPAu-induced mitochondrial alterations were reversed or inhibited by exposure to the sulfhydryl reducing agent, dithiothreitol. Also, the TEPAu-induced collapse of the mitochondrial membrane potential was partially inhibited by dibucaine, a non-specific inhibitor of phospholipases. These data suggest that TEPAu-induced mitochondrial dysfunction is sulfhydryl dependent. TEPAu-induced mitochondrial dysfunction results in dissipation of the potential difference across the inner mitochondrial membrane which inhibits mitochondrial oxidative phosphorylation. The mechanism by which TEPAu induces the collapse of the membrane potential may be mediated by a sulfhydryl-dependent increase in permeability of the inner membrane to protons.

SK&F 104524 (bis-[1,2 bis(diphenylphosphino)-ethane]gold(l) lactate) [( Au(dppe)2]+) is an experimental antineoplastic agent that is hepatotoxic in vivo in the dog as well as highly cytotoxic to isolated canine hepatocytes in vitro. Preliminary studies in isolated dog hepatocytes have indicated that [Au(dppe)2]+ causes an increase in hepatocyte respiration and a decrease in cellular ATP. The purpose of the present investigation was to characterize [Au(dppe)2]+-induced cytotoxicity and biochemical lesions in the intact cell and to correlate these changes with mitochondrial function. The uptake of [14C][Au(dppe)2]+ by rat hepatocytes was rapid, reaching a maximum by 30 min. [Au(dppe)2]+ was distributed throughout the hepatocyte and associated rapidly with mitochondria, nuclei, cytosol and cellular membranes. [Au(dppe)2]+ caused cell lethality in a concentration-dependent fashion; although 5 microM did not cause any changes in lactic dehydrogenase leakage, 20 microM produced 100% cell death by 120 min. [Au(dppe)2]+ also caused concentration-dependent bleb formation of the hepatocyte plasma membrane, increased oxygen consumption and loss of ATP within 30 min. ATP loss was associated with transient increases in AMP and ADP and a profound drop in the ATP/ADP ratio and energy charge. Total nucleotides (adenine and xanthine nucleotides) remained constant. The pattern of glutathione depletion coincided with that of lactic dehydrogenase leakage. Electron microscopy of hepatocytes exposed to [Au(dppe)2]+ for 30 min revealed depletion of glycogen granules and marked swelling of mitochondria. In isolated rat liver mitochondria, [Au(dppe)2]+ caused a stimulation of state 4 respiration and loss of the respiratory control ratio. [Au(dppe)2]+ also relieved the oligomycin-induced inhibition of state 3 (ADP-stimulated) respiration.(ABSTRACT TRUNCATED AT 250 WORDS)