title: A possible cyclic AMP-mediated regulation of microsomal fatty acyl-CoA desaturation system in Tetrahymena microsomes.
abstract: Profound alterations in the microsomal fatty acyl-CoA desaturase activities and cyclic AMP production of a unicellular eukaryote, Tetrahymena pyriformis NT-1, originally grown in the glucose-deficient medium, were observed, following the administration of glucose or beta-adrenergic agonists such as epinephrine and isoproterenol. There was a great increase of stearoyl-CoA (delta 8) desaturase activity coincident with a 2-fold decrease of oleoyl-CoA (delta 12) desaturase activity over the first 2 h after administration of these compounds. During this period of time, it was found that the production in vivo of labeled oleic acid from [14C]acetic or [3H]palmitic acid increases 2-fold and the formation in vivo of each labeled linoleic and gamma-linolenic acids drastically decreases. Glucose or beta-adrenergic agonists caused an increase of stearoyl-CoA-stimulated reoxidation rate of NADH-reduced cytochrome b5 but depressed oleoyl-CoA-stimulated reoxidation rate of b5, indicating that both desaturase activities are controlled by the respective terminal components of the desaturase system. A significant and reproducible increase of adenylate cyclase activity and a slight decrease of cyclic AMP phosphodiesterase activity were observed to occur within the first 2 h after the addition of these compounds, when cyclic AMP content in Tetrahymena cell rose by 3-4-fold. Propranolol, a beta-adrenergic blocker, abolished the effects of glucose or beta-adrenergic agonists on the activities of fatty acyl-CoA desaturases and the terminal components as well as cyclic AMP production of cells. These results suggest that glucose and beta-adrenergic agonists may modulate the microsomal fatty acyl-CoA desaturase system in Tetrahymena by acting through the increase of intracellular cyclic AMP content.
authors.forename: S
authors.initials: S
authors.lastname: Umeki
authors.forename: Y
authors.initials: Y
authors.lastname: Nozawa
mesh_terms: D015105:3',5'-Cyclic-AMP Phosphodiesterases / Q000378:metabolism; D000085:Acetates / Q000378:metabolism; D019342:Acetic Acid; D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D000242:Cyclic AMP / Q000502:physiology*; D004837:Epinephrine / Q000494:pharmacology; D044943:Fatty Acid Desaturases / Q000378:metabolism*; D005227:Fatty Acids / Q000378:metabolism; D005947:Glucose / Q000494:pharmacology; D007545:Isoproterenol / Q000494:pharmacology; D008861:Microsomes / Q000201:enzymology; D009245:NADH Dehydrogenase / Q000378:metabolism; D009247:NADH, NADPH Oxidoreductases / Q000378:metabolism; D009251:NADPH-Ferrihemoprotein Reductase / Q000378:metabolism; D019308:Palmitic Acid; D010169:Palmitic Acids / Q000378:metabolism; D013230:Stearoyl-CoA Desaturase / Q000378:metabolism; D013769:Tetrahymena pyriformis / Q000187:drug effects / Q000201:enzymology*
chemical_list: D000085:Acetates; D005227:Fatty Acids; D010169:Palmitic Acids; D019308:Palmitic Acid; D000242:Cyclic AMP; D044943:Fatty Acid Desaturases; D013230:Stearoyl-CoA Desaturase; D009247:NADH, NADPH Oxidoreductases; D009251:NADPH-Ferrihemoprotein Reductase; C014227:ferricyanide reductase; D009245:NADH Dehydrogenase; D015105:3',5'-Cyclic-AMP Phosphodiesterases; D000262:Adenylyl Cyclases; D005947:Glucose; D007545:Isoproterenol; D019342:Acetic Acid; D004837:Epinephrine