CHOLESTEROL-SYNTHESIS AND ESTERIFICATION IN ISOLATED ENTEROCYTES - REGULATION BY CHOLESTEROL AND CHOLESTYRAMINE FEEDING

The purpose of the present study was to investigate the physiological control of the main regulatory enzymes of cholesterol metabolism in is olated enterocytes obtained from chick duodenum, jejunum and ileum. Ch olesterol feeding resulted in an inhibition of 3-hydroxy-3-methyl-glut aryl-CoA reductase and mevalonate 5-pyrophosphate decarboxylase, while cholestyramine feeding increased reductase activity in all the region s studied and decarboxylase activity only in duodenum. Cholesterol fee ding markedly increased acyl-CoA:cholesterol acyltransferase, but the effects of cholestyramine were less clear. The effects on transferase activity cannot be due to differences in the availability of acyl-CoA as exogenous substrate as no significant differences were found in acy l-CoA hydrolase activity after any of the dietary treatments. The effe cts of cholesterol feeding were related to changes in the cholesterol content of epithelial cells, whereas in the case of cholestyramine thi s relationship was less apparent.