Effects of injecting exogenous lipid transfer protein into rats

Rats were injected intravenously with preparations of partially purified lipid transfer protein isolated from human plasma. Cholesteryl ester transfer activity disappeared from the plasma of recipient rats with a t1/2 of about 10 h and after 24 h had fallen to a level comparable to that in human plasma. By contrast there was no measurable cholesteryl ester transfer activity in the plasma of control rats. Plasma collected from rats 24 h after the injection was subjected to ultracentrifugation at 1.225 g/ml; lipoproteins in the 1.225 g/ml supernatant were subsequently separated by both gel filtration chromatography and gradient gel electrophoresis. The major change in the treated animals was a total loss of the large, cholesteryl ester-rich, apolipoprotein E-rich high-density lipoproteins, HDL1, which are prominent in the plasma of control rats. This loss of HDL1 unmasked an obvious peak of low-density lipoproteins that had been obscured in the control rats. Other changes in the treated rats included an increase in the relative cholesteryl ester content of very-low-density lipoproteins and the emergence of a peak of triacylglycerol in the high-density lipoproteins.