title: The effects of diphenyleneiodonium on mitochondrial reactions. Relation of binding of diphenylene[125I]iodonium to mitochondria to the extent of inhibition of oxygen uptake.
abstract: 1. Several ring-substituted derivatives of diphenyleneiodonium catalyse the exchange of Cl- and OH- ions across the inner membrane of rat liver mitochondria. They also inhibit state 3 and state 3u oxidations of glutamate plus malate in the presence of Cl- more than in its absence. Most have activities similar to diphenyleneiodonium, although 2,4-dichlorodiphenyleneiodonium is up to 50 times more active. 2. Diphenyleneiodonium inhibits soluble rat liver NADH dehydrogenase and NADH oxidation by rat liver sub-mitochondrial particles directly; 2,4-dichlorodiphenyleneiodonium is only about twice as inhibitory. 3. Liver mitochondria contain two classes of binding sites for diphenylene[125I]iodonium, namely high-affinity sites with an affinity constant of 3 X 10(5) M-1 (1--2 nmol/mg of protein), and low-affinity sites with an affinity constant of 1.3 X 10(3) M-1 (80 nmol/mg of protein). Both sites occur in hepatocytes with a relative enrichment of the low-affinity site. Nadh dehydrogenase preparations only apparently contain high-affinity binding sites. Only low-affinity sites occur in erythrocytes. 4. 2,4-Dichlorodiphenyleneiodonium competes with diphenylene[125I]iodonium for both low- and high-affinity sites, whereas tri-n-propyltin only competes for the low-affinity sites. 5. The high-affinity sites are apparently associated with NADH dehydrogenase and the low-affinity sites probably represent electrostatic binding of diphenylene[125I]iodonium to phospholipids. The high-affinity site does not appear to be associated with a rate-limiting stage of NADH oxidation.
mesh_terms: D000818:Animals; D001665:Binding Sites; D001692:Biological Transport / Q000187:drug effects; D002712:Chlorides / Q000378:metabolism; D004912:Erythrocytes / Q000378:metabolism; D006801:Humans; D006843:Hydrocarbons, Chlorinated / Q000494:pharmacology; D006847:Hydrocarbons, Iodinated / Q000378:metabolism / Q000494:pharmacology*; D008099:Liver / Q000378:metabolism; D008930:Mitochondria, Liver / Q000187:drug effects* / Q000378:metabolism; D008933:Mitochondrial Swelling / Q000187:drug effects; D009247:NADH, NADPH Oxidoreductases / Q000037:antagonists & inhibitors / Q000378:metabolism; D009861:Onium Compounds / Q000378:metabolism / Q000494:pharmacology; D010101:Oxygen Consumption / Q000187:drug effects*; D051381:Rats
chemical_list: D002712:Chlorides; D006843:Hydrocarbons, Chlorinated; D006847:Hydrocarbons, Iodinated; D009861:Onium Compounds; C007517:diphenyleneiodonium; D009247:NADH, NADPH Oxidoreductases