Triglycerides and apoproteins in toxemia of pregnancy

In order to clarify the mechanism of hypertriglyceridemia caused by toxemia of pregnancy, apoprotein B, CII, CIII, and E in serum were determined by single radial immunodiffusion, and apoprotein CIII0, CII, CIII1 and CIII2 in very low density lipoprotein (VLDL) fractionated by ultracentrifugation were quantified by analytical isoelectric focusing. The increase in triglycerides in toxemia of pregnancy was estimated in VLDL and low density lipoprotein (LDL), mainly in VLDL. In contrast to the increase in triglycerides, apoprotein B and E, believed to interact with LDL receptors on cell membranes, remained unchanged from levels in normal pregnancy. The lack of correlation between triglycerides and these apoproteins may be related to the increase in triglyceride in VLDL. In toxemia of pregnancy, the relative amounts of apoprotein CII, an activator of lipoprotein lipase, and CIII, an inhibitor of lipoprotein lipase, in serum were similar to those in normal pregnancy, but those in VLDL decreased significantly. This finding suggests that the increase in triglyceride in VLDL was caused by inhibition of VLDL to LDL catabolism. These results suggest that one of the factors which causes hypertriglyceridemia in toxemia of pregnancy is impaired removal of triglyceride, in LDL fraction, but mainly in VLDL fraction.