Discrimination between cholesterol and sitosterol for absorption in rats

• Published in: Journal of lipid research 1988-12, Vol.29 (12), p.1583-1591
• Main Authors: Ikeda, I, Tanaka, K, Sugano, M, Vahouny, G V, Gallo, L L
• Format: Article
• Language: English
• Subjects: Animals; Binding, Competitive; Cholesterol - administration & dosage; Cholesterol - blood; Cholesterol - pharmacokinetics; Esterification; In Vitro Techniques; Intestinal Absorption - drug effects; Lymphatic System - metabolism; Male; Micelles; Microvilli - metabolism; Mucous Membrane - metabolism; Rats; Sitosterols - administration & dosage; Sitosterols - blood; Sitosterols - pharmacokinetics
• ISSN: 0022-2275
• DOI: 10.1016/s0022-2275(20)38409-1

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).