title: Modulation of delta 6 and delta 5 rat liver microsomal desaturase activities by dexamethasone-induced factor.
abstract: This report supports evidence for the existence of a dexamethasone-induced factor that modulates fatty acid desaturase activities. Dexamethasone at a dose of 1 mg/rat produced a significant decrease in microsomal delta 6 and delta 5 desaturation activity 12 h after the injection. Both desaturase activities were depressed by a soluble factor present in the cytosolic fraction of cells, since the supernatant of microsomes separated at 110,000 X g from hormonal-treated rat liver homogenates, added to crude or washed control microsomes, was able to inhibit in vitro linoleic and homo-gamma-linolenic conversion to gamma-linolenic and arachidonic acids, respectively. The inhibitory factor was loosely bound to microsomes, since it was also present in a soluble fraction obtained after washing crude microsomes from dexamethasone-treated rats with a low-ionic-strength solution. Besides, trypsin digestion deactivates the dexamethasone-induced factor. Therefore, the depressing effect of glucocorticoids on delta 6 and delta 5 desaturation capacity depends on an unchanged protein structure present in the cytosolic fraction of the cell and whose biosynthesis is brought about by hormonal induction.
mesh_terms: D000818:Animals; D003600:Cytosol / Q000378:metabolism; D000090943:Delta-5 Fatty Acid Desaturase; D003907:Dexamethasone / Q000494:pharmacology*; D044943:Fatty Acid Desaturases / Q000378:metabolism*; D007700:Kinetics; D050602:Linoleoyl-CoA Desaturase; D008099:Liver / Q000378:metabolism; D008297:Male; D008862:Microsomes, Liver / Q000201:enzymology*; D051381:Rats; D011919:Rats, Inbred Strains; D014357:Trypsin / Q000494:pharmacology
chemical_list: D000090943:Delta-5 Fatty Acid Desaturase; D003907:Dexamethasone; D044943:Fatty Acid Desaturases; D050602:Linoleoyl-CoA Desaturase; D014357:Trypsin