The effect of pyrrolnitrin on mitochondrial reactions: the induction of swelling.

An antifungal antibiotic, pyrrolnitrin, was found to show very similar biological activities to those of imidazole antimycotics on isolated mitochondria. Pyrrolnitrin caused drastic swelling of mitochondria in isotonic solutions of alkali metal salts and of sucrose without any addition of substrate for the respiratory chain in mitochondria. The swelling induced by pyrrolnitrin was characterized by a biphasic swelling process; a very fast initial swelling and thereafter a very slow speed secondary swelling. The increase of pyrrolnitrin concentration exponentially increased the magnitude of over-all rapid swelling. Pyrrolnitrin enhance the latent ATPase activity of mitochondria at the similar range of concentrations to those needed for the induction of the swelling. The concentrations of pyrrolnitrin where mitochondrial swelling was induced were found to be far lower than those needed for the exhibition of inhibitory effect on the electron transport system of mitochondria.