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 Δ6 and Δ5 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 × g from hormonal-treated rat liver homogenates, added to crude or washed control microsomes, was able to inhibit in vitro linoleic and homo-γ-linolenic conversion to γ-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 Δ6 and Δ5 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.
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Schedule a callMore From: Biochimica et Biophysica Acta (BBA) - Lipids and Lipid Metabolism
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