Lymphatic absorption and transport of retinol and vitamin D-3 from rat intestine. Evidence for different pathways.
The lymphatic absorption and transport of retinol and vitamin D-3 from rat intestine has been studied. When rats were cannulated in the intestinal lymph duct and given an intraduodenal bolus of [3H]retinol and 14C-labelled vitamin D-3, 14C-labeled vitamin D-3 appeared later in the intestinal lymph than [3H]retinol and the rate of absorption of vitamin D-3 was still maximal at a time when that of retinol had declined. Both vitamins were absorbed via the lymphatic route in association with chylomicrons. Almost all the retinol was esterified, while vitamin D-3 appeared in the chylomicrons as free vitamin D-3. In vitro incubations and in vivo studies using hepatectomized and normal rats showed that the retinyl ester was a relatively nonexchangeable component of the chylomicrons and their remnants. Hence, all the vitamin A followed the remnants in their clearance from plasma. In contrast, significant amounts of vitamin D-3 were transferred from the chylomicrons to other plasma fractions. Therefore, only a fraction of this vitamin may be removed in association with the chylomicron remnants.
D000818:Animals; D002250:Carbon Radioisotopes; D002762:Cholecalciferol / Q000378:metabolism*; D007408:Intestinal Absorption; D007700:Kinetics; D008074:Lipoproteins / Q000302:isolation & purification / Q000378:metabolism; D008196:Lymph / Q000378:metabolism*; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D014316:Tritium; D014801:Vitamin A / Q000378:metabolism*
D002250:Carbon Radioisotopes; D008074:Lipoproteins; D014316:Tritium; D014801:Vitamin A; D002762:Cholecalciferol