Studies on the activity of acyl-CoA:cholesterol O-acyltransferase and acid cholesterol ester synthetase in rat aortas.
Acyl-CoA: cholesterol O-acyltransferase (ACAT) activity was measured in microsomal preparations from rat aorta (intima-media) with [14C]oleoyl CoA and endogenous cholesterol as substrates. The specific activity of ACAT in liver and adrenal microsomal preparations was 10--20-times greater than ACAT activity in aortic microsomes; no ACAT activity could be detected in fat pad microsomes. ACAT activity in liver and adrenal microsomes was enhanced by the addition of exogenous cholesterol. In contrast, exogenous cholesterol did not increase ACAT activity in rat aortic microsomes. Levels of endogenous cholesterol and ACAT activity in microsomal preparations from rat aorta were not reduced when circulating plasma cholesterol levels were decreased by the administration of 4-aminopyrazolopyrimidine to rats. Acid cholesterol ester synthetase activity was not detectable in high-speed supernatant fractions from rat aorta; low levels of activity could be measured in rat aorta microsomal preparations but this was less than 10% of ACAT activity. Thus, ACAT would seem to be the principal enzymatic route for the synthesis of cholesterol esters in aorta.
D000217:Acyltransferases / Q000378:metabolism*; D000273:Adipose Tissue / Q000201:enzymology; D000311:Adrenal Glands / Q000201:enzymology; D000818:Animals; D001011:Aorta / Q000201:enzymology*; D002265:Carboxylic Ester Hydrolases / Q000378:metabolism*; D002784:Cholesterol / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008099:Liver / Q000201:enzymology; D008297:Male; D008861:Microsomes / Q000201:enzymology; D011817:Rabbits; D051381:Rats; D002787:Sterol Esterase / Q000378:metabolism*; D002785:Sterol O-Acyltransferase / Q000378:metabolism*; D013379:Substrate Specificity; D013552:Swine
D002784:Cholesterol; D000217:Acyltransferases; D002785:Sterol O-Acyltransferase; D002265:Carboxylic Ester Hydrolases; C031695:acid cholesterol ester synthetase; D002787:Sterol Esterase