Tatsuo Ishida

Cooperative effect of sulfite and vanadium compounds on lipid peroxidation

Abstract The cooperative mechanism of the action of sulfite and metal compounds on lipid peroxidation was investigated in vitro. Results obtained were as follows: (1) Lipid peroxidation of rat lung extracts, liver microsomes, and mitochondria was induced by sulfite, depending on its concentration. Peroxidation was accelerated remarkably by metal compounds such as iron or vanadium. (2) The increased lipid peroxidation by sulfite and vanadium was inhibited effectively by free radical scavengers such as hydroquinone, α-tocopherol, or superoxide dismutase. (3) Similar effect of these radical scavengers was seen in lipid peroxidation induced by superoxide anion radical. (4) In the presence of sulfite and vanadium, a significant lysis of human erythrocytes was caused, suggesting an additive action of the effect of these substances.

Effects of phthalate esters on mitochondrial oxidative phosphorylation in the rat.

Effects of Phthalate Esters on Mitochondrial Oxidative Phosphorylation in the Rat. Inouye, B., Ogino, Y., Ishida, T., Ogata, M., and Utsumi, K. (1978). Toxicol. Appl. Pharmacol. 43 , 189–198. The effects of phthalate esters on oxidative phosphorylation and related functions of isolated rat liver mitochondria were examined. Of the phthalate esters examined, di- n -propylphthalate ester, di-isopropyl phthalate ester, di- n -butyl phthalate ester (DNBP), and di-isobutyl phthalate ester, strongly inhibited both respiratory control and ADP:O ratio with increasing state 4 respiration and decreasing state 3 respiration. DNBP also activated the mitochondrial latent ATPase activity. DNBP induced K + release from mitochondria, suggesting its interaction with the mitochondrial membrane and causing a change in permeability to ions. It was concluded that DNBP primarily acts as an uncoupler of the mitochondrial oxidative phosphorylation rather than as an electron transport or an energy transfer inhibitor.

Participation of superoxide free radical and Mn2+ in sulfite oxidation☆

Sulfurous acid gas is a well-known air pollutant. The participation of superoxide (O2•), a species of activated oxygen, in sulfite oxidation was investigated in relationship to this health hazard. The reduction of nitroblue tetrazolium (NBT) was markedly accelerated in the presence of the xanthine-xanthine oxidase system (X-XO), Mn2+ and SO32−, but not by X-XO and Mn2+ or X-XO and SO32− alone. This accelerated NBT reduction was partially suppressed by superoxide dismutase and was completely suppressed by allopurinol. Oxygen consumption was also markedly accelerated under to condition which caused the increase in NBT reduction. Lipid peroxidation of rat liver homogenate increased in the presence of X-XO, SO32−, or both. This increased lipid peroxidation was definitely suppressed by Mn2+. From these observations, it is suggested that chain reactions involving sulfite oxidation are initiated by O2− generated from X-XO, and Mn2+ acts as a catalyst in the process.

Effects of aromatic bromine compounds on the function of biological membranes

The effect of 2,2-bis(3′,5′-dibromo-4′-hydroxyphenyl)propane (tetrabromobisphenol A; TBBP), one of the organic bromine compounds which is used as a plasticizer, a flame-retardant of epoxy resins, or an intermediate for various chemical syntheses, on the function of biological membranes was examined, and the following results were obtained. (1) Incubation of erythrocytes with TBBP resulted in K+ release from the cells and then hemolysis. In this process, erythrocytes change their shape from normal to cup-formed cells and then spherocytes, depending on the TBBP concentration. (2) TBBP also induced K+ release from isolated mitochondria. A low concentration of TBBP, less than 50 μm, increased state 4 respiration and decreased state 3 respiration, resulting in decreases of both respiratory control and oxidative phosphorylation. However, a higher concentration of TBBP, above 100 μm, acted as a respiratory inhibitor. TBBP inhibited the Ca2+ accumulation in mitochondria accompanied by oxygen uptake and stimulated mitochondrial latent ATPase activity. These data indicate that TBBP primarily alters the permeability of membranes, resulting in hemolysis of erythrocytes accompanied by morphological change and uncoupling of the mitochondrial oxidative phosphorylation.