Abstract
Photodynamic action of phloxine on mitochondrial respiration was examined, using rat liver mitochondria. Rat liver mitochondria were suspended in a medium containing phloxine, and irradiated with visible light in the presence of oxygen. The respiratory activities of the photooxidized mitochondria were assayed. The results are summarized as follows. (1) Phloxine-sensitized photooxidation of mitochondria inhibited 2, 4-dinitrophenol (2, 4-DNP)-released respiration. It can be deduced, from an approximate calculation, that the released respiration was inhibited by 10% as every 3 nmoles of oxygen per mg of mitochondrial protein was consumed by photooxidation. (2) Phloxine-sensitized photooxidation of mitochondria released the suppressed respiration. The supernatant obtained by centrifugation of photooxidized mitochondria also released the suppressed respiration of intact mitochondria. This suggests that certain uncoupling factors were released from photooxidized mitochondria. Uncoupling factor in question may be unsaturated fatty acids or U-factor, because bovine serum albumin abolished the respiration-releasing effect of the supernatant of photooxidized mitochondria.
