Alpha-lipoprotein heterogeneity in serum of mammals

Heterogeneity of serum lipoproteins during the fetal and neonatal development of the pig

Serum lipoproteins from fetal, neonatal and adult pigs were characterized with the use of lipid analysis, polyacrylamide gradient gel electrophoresis, two-dimensional immunoelectrophoresis and zonal ultracentrifugation. Almost all serum cholesterol was found in LDL during the early stages of fetal development, while low but increasing levels appeared in the fetal pig HDL by the end of the gestation period. In the fetal pig, most of the serum triglycerides could be found in the HDL fraction. After the start of suckling, the levels of serum triglycerides and cholesterol increased. Most of these exogenous lipids were found in the chylomicrons + VLDL + LDL fraction of the newborn pig serum. The molecular weights of the native serum lipoproteins were calculated as being 2.0-2.4 X 10(5) daltons for newborn pig HDL and 1.4-1.7 X 10(6) daltons for newborn pig LDL. Minor changes in the molecular weight distributions were detected within these ranges for both HDL and LDL during fetal and neonatal development of the pig. Zonal ultracentrifugation of neonatal pig serum partly separated the LDL into three subfractions, whereas neonatal HDL appeared as one broad fraction.