The dietary control of the microsomal stearyl CoA desaturation enzyme system in rat liver

Abstract

The response of the stearyl CoA desaturation enzyme system of rat liver microsomes to dietary conditions was studied in detail. The activity which had been decreased by starvation was rapidly induced to a very high level on refeeding of the animals. The activity thus induced returned gradually to the steady-state level on continuation of feeding. During this course, the levels of microsomal electron-transport components were not significantly affected, suggesting that the dietary regulation involved the change of mainly the terminal component of the desaturation system, cyanide-sensitive factor. Injection of cycloheximide not only inhibited the induction but also produced a rapid decay of the microsomal desaturation activity with a half-time of 3-4 hr. On continuous refeeding, a rapid increase in the desaturation activity was first detected on the rough microsomal membrane and then on the smooth membrane about 5 hr later. Actinomycn D depressed the increase in the activity on the rough membrane while that in the smooth membrane still continued for about 6 hr after the drug treatment. The significance of the microsomal electron-transport system, with particular attention to cytochrome b5, is discussed from a viewpoint of the regulatory mechanism of desaturation activity. © 1972.