title: Kinetic alterations of cytochrome c oxidase in carbon tetrachloride induced cirrhotic rat liver.
abstract: In a study of the chronic effects of CCl4 on the respiratory activities of rat liver mitochondria, the content of cytochrome c oxidase increased from 0.077 +/- 0.010 (nmol/mg protein) for normal rats to 0.101 +/- 0.009, and its specific activity increased from Vmax = 345 +/- 24 (e-/s/cytochrome aa3) to 431 +/- 19 in mitochondria of CCl4 treated rats. There was a slight increase in Km for cytochrome c from 5.63 +/- 0.08 microM to 7.79 +/- 0.80. These results would strongly suggest that an appreciable decrease in the steady state concentration of ATP in hepatic cells of CCl4 treated rats brought about a compensatory increase in the overall activity of cytochrome c oxidase. However, when the rate of oxygen uptake by mitochondria was measured in the presence of rotenone and tetramethyl-p-phenylene-diamine with NADH as substrate, the specific activity in CCl4 treated rats was lower than that of normal rats (Vmax = 345 +/- 31 (e-/s/cytochrome aa3), as compared to Vmax = 408 +/- 21) in spite of the increased activity of cytochrome c oxidase. This phenomenon was ascribed to a decrease in the activity of NADH cytochrome b5 reductase in the mitochondrial outer membrane due to CCl4 treatment.
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002251:Carbon Tetrachloride / Q000633:toxicity*; D003579:Cytochrome Reductases / Q000378:metabolism; D042966:Cytochrome-B(5) Reductase; D003576:Electron Transport Complex IV / Q000378:metabolism*; D007700:Kinetics; D008106:Liver Cirrhosis, Experimental / Q000139:chemically induced* / Q000201:enzymology; D008297:Male; D008930:Mitochondria, Liver / Q000187:drug effects / Q000201:enzymology*; D009243:NAD / Q000378:metabolism; D009245:NADH Dehydrogenase / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D012402:Rotenone / Q000494:pharmacology; D013772:Tetramethylphenylenediamine / Q000494:pharmacology
chemical_list: D012402:Rotenone; D009243:NAD; D000255:Adenosine Triphosphate; D002251:Carbon Tetrachloride; D003579:Cytochrome Reductases; D042966:Cytochrome-B(5) Reductase; D009245:NADH Dehydrogenase; D003576:Electron Transport Complex IV; D013772:Tetramethylphenylenediamine