The effect of feeding and fasting on the activity of acyl-CoA:cholesterol acyltransferase in rat small intestine

Abstract

This study investigated whether the microsomal acyl-CoA:cholesterol acyltransferase (ACAT) in rat small intestine is regulated under physiological conditions. Two previously described in vitro assays were used, both based on the esterification of endogenous cholesterol with exogenous acyl-CoA, preformed or generated during the incubation. The important and consistent finding with rats on normal diet was an increase in ACAT activity with fasting and a decrease with feeding. Independent of the assay used, the ratio between ACAT activity in night-fasted and night-fed animals was .apprx. 2 (P < 0.005). When the fasting period was extended to 36 h of a corresponding difference was found whether the ACAT assay was based on preformed [1-14C]oleoyl- or [1-14C]palmitoyl-CoA as acyl-donor (P < 0.05). The microsomal content of unesterified cholesterol was higher in fasted than fed animals, suggesting that availability of this substrate might be a factor in the regulation of rat intestinal ACAT activity.