Some aspects of mechanism of inhibition of cholesterol absorption by beta-sitosterol.
Mixed bile salt micelle solubilized either cholesterol or beta-sitosterol to a comparable extent. When added simultaneously, beta-sitosterol restricted the micellar solubility of cholesterol. beta-Sitosterol also reduced the cholesterol content in the aqueous (micellar) phase of the intestinal contents of rats, the extent of reduction being comparable with that observed in vitro. The intestinal uptake of cholesterol in vivo was equivalent to the micellar incorporation of cholesterol both in vitro and in vivo. beta-Sitosterol had no inhibitory effect on cholesterol absorption from the micellar solution in jejunal loops in situ, whereas the rate of beta-sitosterol uptake was only about one-fifth that of cholesterol. The intestinal uptake of beta-sitosterol intubated into the stomach of rats was about one-fifth that of cholesterol. The intestinal brush-border membrane discriminated these sterols. These results suggest that the restriction of the micellar solubility of cholesterol, rather than the inhibition of uptake from brush-border membrane, is the major determinant for the interference of beta-sitosterol with cholesterol absorption.
D000818:Animals; D002250:Carbon Radioisotopes; D002784:Cholesterol / Q000378:metabolism*; D007408:Intestinal Absorption / Q000187:drug effects*; D007413:Intestinal Mucosa / Q000187:drug effects / Q000378:metabolism; D007583:Jejunum / Q000378:metabolism; D007700:Kinetics; D008297:Male; D008823:Micelles; D051381:Rats; D011919:Rats, Inbred Strains; D012855:Sitosterols / Q000378:metabolism / Q000494:pharmacology*
D002250:Carbon Radioisotopes; D008823:Micelles; D012855:Sitosterols; C025473:gamma-sitosterol; D002784:Cholesterol