Hepatic uptake of phospholipid-depleted chylomicrons in vivo. Comparison with the uptake of chylomicron remnants

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Abstract
Rats pretreated with Triton WR-1339 to prevent the formation of remnants were injected with [3H]cholesterol-labeled remnants, intact chylomicrons or chylomicrons depleted most of their surface phospholipids by treatment with phospholipase A2. Within 5 min .apprx. 80% of the injected label of remnants and phospholipid-depleted chylomicrons was incorporated into the livers compared with < 10% of the injected radioactivity of intact chylomicrons. A similar rapid hepatic uptake of radioactivity occurred when rats not pretreated with Triton were injected with [3H]cholesterol-labeled phospholipid-depleted chylomicrons. This rapid hepatic uptake of phospholipid-depleted chylomicrons occurred apparently without any alteration in the apoprotein composition of the particles. The participation of hepatocytes in the uptake of remnants and phospholipid-depleted chylomicrons was examined. Both types of particles were taken up by the hepatocytes. Small chylomicrons (Sf [Sverdberg flotation unit] < 400) were taken up more efficiently than were large chylomicrons (Sf > 400), but neither was taken up as efficiently as the remnants. Phospholipid-depleted chylomicrons and chylomicron remnants are apparently taken up by the liver by a similar mechanism, which depends on the loss of surface phospholipids.

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