Discrimination between cholesterol and sitosterol for absorption in rats.
The intestinal absorption of cholesterol and sitosterol was compared in rats. The intragastric administration of a single emulsified lipid meal containing either 50 mg of [4-14C]cholesterol or [4-14C]sitosterol resulted in the lymphatic absorption of 18.2% and 0.42% of each sterol, respectively, in 6 hr. This difference was unaltered when the mucosal sterol load was equalized by reducing the cholesterol to 1 mg in the emulsified lipid meal while maintaining the same sitosterol load or when the physical state in the lumen was equalized by infusion of a micellar solution containing both sterols into bile-diverted intestine. Lymphatic cholesterol was 90% esterified compared to 12% for sitosterol. Both sterols were associated predominantly (greater than 70%) with the chylomicron fraction. Eighty percent of the chylomicron cholesterol was recovered as ester with the core lipids, while 77% of the sitosterol was recovered as free sterol with the chylomicron coat. In mucosal homogenates at 6 hr, sitosterol recovery was one-eleventh that of cholesterol. When [3H]cholesterol (10 mg) and [14C]sitosterol (10 mg) were co-administered in an emulsified intragastric lipid meal, sitosterol associated with the brush border isolated 2 hr later was one-fifth that of cholesterol. Similar differences were seen when brush border membranes were incubated in vitro with micellar solutions containing either 50 microM [3H]cholesterol or [14C]sitosterol and the relative uptake of each sterol was unaffected by micellar phospholipid type (egg yolk phospholipids, phosphatidylcholine, or phosphatidylethanolamine).(ABSTRACT TRUNCATED AT 250 WORDS)
Ikeda
I
I
Department of Biochemistry, George Washington University, School of Medicine, Washington, DC 20037.
Tanaka
K
K
Sugano
M
M
Vahouny
G V
GV
Gallo
L L
LL
D000818:Animals; D001667:Binding, Competitive; D002784:Cholesterol / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*; D004951:Esterification; D066298:In Vitro Techniques; D007408:Intestinal Absorption / Q000187:drug effects; D008208:Lymphatic System / Q000378:metabolism; D008297:Male; D008823:Micelles; D008871:Microvilli / Q000378:metabolism; D009092:Mucous Membrane / Q000378:metabolism; D051381:Rats; D012855:Sitosterols / Q000008:administration & dosage / Q000097:blood / Q000493:pharmacokinetics*
D008823:Micelles; D012855:Sitosterols; C025473:gamma-sitosterol; D002784:Cholesterol