Periphral lymphocytes suspended in RPMI-1640 were incubated in plates of 96 wells for 96 hours with 50 ?g/ml of PHA, various concentrations of LDL-ch and0.6 ?M of mevinolin (experimental) or equal volume of its solvent-dimethyl sulfoxide (control). 6 hours before harvesting cells, 0.5?Ci of ~3H-TdR was added to each well, then cells were harvested and their cpm counted. The LDL receptor activity was expressed as mevinolin-mediated lymphocyte proliferation inhibition rate which can be calculated by the following equation:Percent Inhibition Rate=(1-cpm exp./cpm con.)100%.It was found that the lymphocyte proliferation inhibition rate at 5?g/ml of LDL-ch was less than 20% for normal and non-FH hyperlipidemic subjects, 25-55% for FH heterozygotes and over 60% for FH homozygotes. Thus, FH patients were distinguished from normal subjects and non-FH hyperlipidemic patients.

The activity of the solubilized receptor was assayed by precipitating the receptor with acetone in the presnce of egg phosphatidyleholine liposomes. It was found that the binding of ~(125)I-LDL to fetal liver receptors rose significantly with the increase of fetal age. During the same period, the total cholesterol (TC) and LDL-eholesterol (LDL-C) levels in fetal serum declined progressively. The correlation between fetal age and concentration of TC and LDL-C were -0.80(P

The activities of low density lipoprotein (LDL) receptors in 15 organs and tissues from 5 human fetuses of the ages of 22 to 34 weeks were determined using a membrane filter assay of the specific binding of ~(125)I-LDL to tissue homogenates. The results showed that the adrenal cortex (465 ng/mg protein) had the highest activity of ~(125)I LDL specific binding seven times than that of the medulla. Adipose tissue (214 ng/mg protein) and liver (102 ng/mg protein) ranked second. Relatively high bindings were also observed in the skeletal muscle (89 ng/mg protein), brain (65 ng/mg protein), kidney (60 ng/mg protein) and spinal cord (56ng/mg protein). It was found that the activity of LDL receptors in the central nervous system of human fetus was higher than that of cows, of human adultsand of humam fetuses of 16 to 20 weeks as reported by other investigators. Relatively high level of LDL receptor mRNA in human fetal brain was also found by ~(32)P-cDNA probe hybridization analysis. It is suggested that the growing and developing central nervous system of human fetus reqiresmore cholesterol. In addition, We also observed preliminarily that the tendency of LDL receptors activities in liver and adrenal gland cortex were gradually inereased with fetal age.

We observed the catabolic characterestics of in vitro prepared nonenzymatically glucosylated low density lipoprotein (glcLDL) in mouse peritoneal macrophages (M?) and human monocyte line (U_(937); and found that glcLDL did not stimulate the increase degradation of glcLDL significantly nor did the accumulation of glcLDL cholesterol in mouse peritoneal M?. However the degradation of glcLDL by U_(937) cells was positively proportional to the concentration of glcLDL. The pre-treatment of U_(937) cells with 12-O-tetradecanoylphorbol 13-acetate (TPA) increased the degradation of glcLDL and was also positively proportional to the concentration of glcLDL. The relationship between these phenomena and the accelerated developement of atherosclerosis in diabetes mellitus was discussed.