Compositional changes and apoprotein A-I metabolism of plasma high density lipoprotein in estrogenized chicks

The effect of estrogen on compositional changes, apolipoprotein (apo) A-I metabolism and the morphology of plasma high density lipoprotein (HDL) were investigated in chicks. The administration of 17 beta-estradiol (25 mg/kg body weight) to growing male chicks (8-week-old) markedly reduced the concentrations of plasma HDL components, except for triglyceride (TG). At the same time, levels of TG, total cholesterol (TC) and phospholipid (PL) in plasma were greatly elevated. The respective values for TG, TC, PL and protein in HDL were 13.9, 89.3, 154.1 and 231.7 (mg/dL) in the control, and 39.0, 35.1, 113.8 and 160.0 (mg/dL) in chicks upon estrogen treatment for one day. In vivo kinetic studies showed that the fractional catabolic rate of HDL apo A-I was significantly higher (p less than 0.05) in estrogen-treated chicks than in control birds, indicating an increased efficiency of HDL removal in the former. The production rate of HDL apo A-I also was significantly lower (p less than 0.05) in estrogen-treated chicks. Sodium dodecyl sulfate-acrylamide gel electrophoresis followed by laser scanning densitometry of HDL apolipoproteins in estrogen-treated chicks revealed a reduction of apo A-I and the occurrence of new apolipoproteins which had been absent in HDL of untreated birds. The HDL particles showed that the mean particle size of HDL became larger upon estrogen treatment. Particles with diameters between 70 and 123 A were predominant in HDL of control chicks, while particles with diameters between 97 and 143 A were most abundant in HDL of estrogen-treated chicks.