Changes in plasma lipoprotein constituents during constant infusions of heparin.

Constant infusions of heparin of 4 to 6 hours' duration were used to estimate the transfer of very low density lipoprotein constituents to other plasma lipoproteins. Eleven subjects were studied, 3 with Type III and the remainder with either Type IV or V hyperlipoproteinemia. Whereas only about 5% of the triglyceride lost from VLDL was recovered in the other lipoproteins, 44% of the cholesterol was retained in the circulation, in equal amounts within low density (d 1.019-1.063) and intermediate density (d 1.006-1.019) lipoproteins. By contrast, there was no apparent loss of protein, more than half of that originally in VLDL being recovered in high density lipoprotein. In subjects with Type III hyperlipoproteinemia, lipid and protein was lost from the intermediate density lipoprotein as well as from VLDL. In subjects with marked hypertriglyceridemia, cholesterol became redistributed from larger to smaller VLDL. The esterification of plasma cholesterol as measured in vitro, was apparently suppressed during the early phase of the heparin infusions, but tended to recover later.