Lipoproteins and lipids in fetal, neonatal and adult rat serum.

Abstract

Levels of the serum lipoproteins (HDL, LDL and VLDL) and lipids in the fetal, neonatal and pregnant rat were measured using electrophoretic, immunological and biochemical methods. The results were compared to those of the adult rat. In the fetal rat at the end of gestation, the lipoprotein pattern was dominated by LDL (beta-lipoprotein). Fetal HDL (alpha-lipoprotein) occurred at a low concentration and showed a lower proportion of cholesterol and a higher proportion of triglycerides than did HDL in the adult rat serum. VLDL (pre-beta-lipoprotein) was present only at very low concentrations. The lipoprotein pattern of suckling neonatal rats showed rapidly increasing levels of VLDL and LDL, and high serum lipid values during the first 2 weeks after birth. The lipoprotein pattern of the adult rat, with the HDL fraction dominating, was completely developed by about 4 weeks after birth. In rats during late pregnancy, very high serum values were found for VLDL and LDL. High levels of triglycerides associated with these fractions were also seen. The serum lipoprotein development of the fetal and neonatal rat is different from that reported for the pig and man. This focuses the interest on the differences in lipid and lipoprotein metabolism between species during ontogenic development.