Metal ion and energy requirements in the triamcinolone-induced swelling of mitochondria

Abstract

The effect of triamcinolone on rat liver mitochondrial swelling has been studied by measuring changes in the optical density at 520 mμ. The action of the steroid is characterized by a rapid initial fall in the optical density which is strictly dependent on the cationic environment; the order of effectiveness of the metal ions is: Li + < Na + < K + = Rb +. The triamcinolone-induced swelling phenomenon takes place in hypertonic solutions, is more marked at high pH, and is diminished by the presence of ammonium in the incubation mixture. Indirect evidence indicates that it is the metal ion which produces the structural change after the steroid has bound to the mitochondria. For a maximum rate of the triamcinolone-induced swelling, high-energy intermediates of oxidative phosphorylation seem to be required. Triamcinolone-swollen mitochondria show a rise in the optical density after the addition of adenosine triphosphate, guanosine triphosphate, inosine triphosphate and heparin, but only if the incubation mixture is at pH 4.0.