Repression by dexamethasone of epinephrine-induced modulation of the fatty acyl-CoA desaturase system in Tetrahymena microsomes.
Epinephrine modulation of the fatty acyl-CoA desaturase activities in Tetrahymena microsomes, namely the stimulation of delta 9 desaturase activity with a decreased activity of delta 12 desaturase, was markedly inhibited by dexamethasone administered 30 min prior to epinephrine addition. This effect by dexamethasone was dose-dependent. With epinephrine or dexamethasone prior to epinephrine administration, the activities of delta 9-terminal and delta 12-terminal components were found to change in parallel with those of delta 9 and delta 12 desaturase activities respectively. Furthermore, addition of dexamethasone as early as 30 min before epinephrine repressed the epinephrine-mediated stimulation of cyclic AMP production and of adenylate cyclase activity. Therefore, it is suggested that dexamethasone may inhibit the modulation by epinephrine of the terminal component activity, which plays a crucial role in microsomal fatty acyl-CoA desaturase system, through the reduction of cyclic AMP accumulation by decreased responsiveness to epinephrine of Tetrahymena cells.
D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D000242:Cyclic AMP / Q000096:biosynthesis; D003907:Dexamethasone / Q000494:pharmacology*; D004579:Electron Transport / Q000187:drug effects; D004837:Epinephrine / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D044943:Fatty Acid Desaturases / Q000378:metabolism*; D008861:Microsomes / Q000201:enzymology; D013769:Tetrahymena pyriformis / Q000201:enzymology*
D003907:Dexamethasone; D000242:Cyclic AMP; D044943:Fatty Acid Desaturases; D000262:Adenylyl Cyclases; D004837:Epinephrine