REGULATION OF CHOLESTEROL UPTAKE IN THE RAT INTESTINAL-CELL LINE

A new model to study cholesterol absorption in the rat intestinal cell s is described. Rat intestine epithelial cells IRD98 were incubated wi th mixed micelles containing bile acid, phospholipid, cholesterol or i ts nonabsorbable analogue, sitosterol, and trace amounts of [H-3]chole sterol or [C-14]sitosterol. Cholesterol and sitosterol uptake was then determined following lipid extraction; specific cholesterol uptake wa s determined as the difference between cholesterol and sitosterol upta ke. Cholesterol, but not sitosterol, uptake was time- and dose-depende nt and saturable. Loading of cells with non-lipoprotein cholesterol re duced cholesterol, but not sitosterol, uptake in a dose-dependent mann er. In contrast, treatment of cells with an inhibitor of cholesterol s ynthesis, lovastatin, stimulated cholesterol, but not sitosterol, upta ke in a dose-dependent manner. Treatment of cells with palmitic, capro ic and oleic acids up-regulated specific cholesterol uptake, while lin oleic and stearic acids had an opposite effect. None of the fatty acid s affected sitosterol uptake.