Intestinal absorption and lymphatic transport of cholesterol and beta-sitostanol in the rat

The intestinal absorption of cholesterol and beta-sitostanol (the saturated analogue of beta-sitosterol) were measured and their absorptions compared in the presence and absence of cholestyramine. After test meals containing [(3)H]cholesterol and [(14)C]beta-sitostanol without added cholestyramine, 4-day fecal collections yielded an average of 51% of the fed cholesterol and 83% of the fed beta-sitostanol. In separate lymph transport studies without cholestyramine, 36% of the fed cholesterol was recovered in lymph in 24 hours compared to only 2% of the fed beta-sitostanol. Thus, while total recoveries of the two labeled compounds in feces plus lymph were nearly identical (51% + 36% = 87% for cholesterol and 83% + 2% = 85% for beta-sitostanol) their distribution in the two compartments was markedly different, reflecting the relative nonabsorbability of beta-sitostanol. Adding cholestyramine to the test meal caused fecal excretion of cholesterol to increase to 73%, independent of the dose of cholestyramine used. Cholestyramine had no effect on the fecal excretion of beta-sitostanol (average excretion after cholestyramine, 85%). The relative non-absorbability of beta-sitostanol compared to cholesterol is clearly evident in this study and leads us to suggest its possible use as a lipid-soluble, nonabsorbable reference compound for measurement of the absorption of cholesterol and other lipids. Further data are presented to justify its use for this purpose.-Hassan, A. S., and A. J. Rampone. Intestinal absorption and lymphatic transport of cholesterol and beta-sitostanol in the rat.