Chemical and isotopic measurement of cholesterol absorption in the rat.
Data are presented on cholesterol absorption in 6 non-fasted lymph duct-cannulated rats during continuous infusion of oil or oil plus cholesterol (mass + isotope). Endogenous thoracic duct lymph cholesterol averaged 2 mumoles/h during infusion of triolein. Lymph cholesterol flux increased to 3.3 mumoles/h during infusion of oil plus a low dose of cholesterol (1.7 mumoles/h), to 4.8 mumoles/h at a medium dose (4.4 mumoles/h) and to 8.9 mumoles/h during infusion of a high dose of cholesterol (30 mumoles/h). The transport of endogenous cholesterol was significantly decreased by the high infusion rate of cholesterol. At each level of cholesterol infusion, about 90% of the increase in lymph cholesterol was due to cholesteryl ester. Radioactive cholesterol significantly under-estimated the percent of cholesteryl ester in the increased cholesterol flux due to cholesterol infusion, especially at the low dose. The percent of infused radioactive cholesterol absorbed was a fairly accurate monitor of the increase in lymph cholesterol due to the exogenous loads. However, small numerical discrepancies at the medium and high doses suggest that the use of isotopic cholesterol to measure cholesterol absorption in careful balance studies may have limitations.
D000818:Animals; D001692:Biological Transport; D002250:Carbon Radioisotopes; D002784:Cholesterol / Q000032:analysis; D002788:Cholesterol Esters / Q000032:analysis; D002791:Cholesterol, Dietary / Q000378:metabolism*; D002855:Chromatography, Thin Layer; D007408:Intestinal Absorption; D007553:Isotope Labeling; D008196:Lymph / Q000032:analysis / Q000378:metabolism*; D008643:Mesentery; D051381:Rats; D013897:Thoracic Duct; D014316:Tritium
D002250:Carbon Radioisotopes; D002788:Cholesterol Esters; D002791:Cholesterol, Dietary; D014316:Tritium; D002784:Cholesterol