Effects of cystamine and cysteamine on the adenosine-triphosphatase activity and oxidative phosphorylation of rat-liver mitochondria

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Abstract
Cystamine(2,2[image]-diaminodiethyl disulphide) caused an unmasking of mitochondrial adeno-sine triphosphatase and a leakage of Mg2+ from the mitochondria, and decreased the stimulation of adenosine triphosphatase by 2,4-dinitro-phenol. When Mg2+ was added, cystamine potentiated the activation of adenosine triphosphatase by 2,4-dinitrophenol. Cystamine was without effect on the adenosine triphosphatase of disrupted mitochondria. Cystamine was moderately potent as an uncoupling agent and as an inhibitor of the [p32] P1-ATP exchange reaction. Cysteamine (2-aminoethanethiol) was without the above effects, when special precautions were taken to counteract its autoxidation. The effects of cystamine should probably be ascribed to its disulphide group, since the diamine cadaverine protected slightly against the loss of Mg2+ and the decrease of 2,4-dinitrophenol-stimulated adenosine-triphosphatase activity caused by aging of the mitochondria. It is suggested that cystamine acts by a breakdown of mitochondrial permeability barriers.