A dexamethasone-induced protein stimulates delta 9-desaturase activity in rat liver microsomes

The effect of dexamethasone on the oxidative desaturation of [1-14C]palmitic to palmitoleic acid on rat liver microsomes, was studied. After 12 h of dexamethasone injection (1 mg/rat) a significant increase in delta 9-desaturase activity, was observed. This effect was also produced by a factor present in a 110,000 X g supernatant soluble fraction obtained after washing crude microsomes from dexamethasone-treated rats with a low ionic strength solution. The dexamethasone-induced factor was present not only in the liver cytosolic fraction of treated animals but also in the cytosol of isolated HTC cells previously incubated with the hormone. Dexamethasone would act via a newly synthesized modulatory factor. The effect depends on an unchanged protein structure, since its biological activity is impaired by trypsin digestion.