Role of the intestine in chylomicron remnant clearance.

When 810 mumol of [3H]glyceryl trioleate (TO) were infused intraduodenally over 6 h into rats, 29% of the triacylglycerol (TG) acyl groups in the mucosa were not from the infusate. We tested the hypothesis that chylomicron remnants contribute to the mucosal pool of nondietary TG acyl groups, since the acyl group composition of the chylomicron remnants was 58% oleate, compared with 90% in their parent chylomicrons. Purified 3H-labeled remnants were generated from chylomicrons formed in rats receiving TO intraduodenally, with 95% of the remnant disintegrations per minute (dpm) being in TG. The 3H-remnants were infused intravenously into rats receiving either saline or 135 mumol/h TO intraduodenally. In the saline-infused rats, 32% of the infused 3H dpm were in the proximal and 19% in the distal intestine and 32% were in the liver. In the fat-infused rats, 12% of the infused 3H dpm were in the proximal and 5% were in the distal gut and 29% were in the liver. When [3H]cholesterol-labeled remnants were infused intravenously and saline was infused intraduodenally, the percentage uptake into the mucosa was nearly the same as with the TG label, but comparable uptake by the liver increased. We conclude that the intestine competes with the liver for chylomicron remnant TG and cholesterol.