DIETARY CHOLESTEROL AS HIGH DENSITY LIPOPROTEIN METABOLISM REGULATOR IN RABBITS

新西兰大白兔出现高胆固醇血症， 饮食时的高脂蛋白血症和动脉粥样硬化 含1%(w/w)胆固醇4-8周。占主导地位的 这种胆固醇引起的高脂蛋白血症的特征是 β-极低密度脂蛋白(β-VLDL)的出现， 一种致动脉粥样硬化的血浆脂蛋白颗粒，富含 载脂蛋白E(ApoE)和胆固醇酯(CE)。还有就是 高密度脂蛋白(HDL)水平显著降低 喂饲胆固醇的兔的血浆。高密度脂蛋白颗粒是反 可致动脉粥样硬化，富含载脂蛋白A-1(apoA-1)和CE。 这项研究计划的目的是提供一种生化 高密度脂蛋白颗粒在胆固醇中消失的解释- 喂兔子。它们的消失可能是由于 合成或分解代谢增加，或两者兼而有之。HDL2和 高密度脂蛋白组分的HDL3亚组分将由 聚丙烯酰胺凝胶电泳法和聚阴离子沉淀法 技巧。凝胶将用密度计扫描，然后 正常和高胆固醇血症兔的HDL2和HDL3峰面积 将会被比较。此外，胆固醇和载脂蛋白A-1的含量 这两个亚类的高密度脂蛋白将用酶来测量 化验将确定这两个高密度脂蛋白亚类中的哪一个正在下降 在喂胆固醇的兔子身上。他们还将确定载脂蛋白A是否- 1和胆固醇正在从其中一个或两个中消失 粒子以等速运动。因为载脂蛋白A-1和胆固醇 以相同的速度从这两个粒子中的一个或两个消失。 由于apoA-1是高密度脂蛋白组分中的主要载脂蛋白，其 饮食中胆固醇的调节将被用作如何 饮食中的胆固醇正在从这其中的一个或两个中消失 粒子以等速运动。因为载脂蛋白A-1是主要的载脂蛋白 在高密度脂蛋白部分，其受饮食胆固醇的调节将是 用作研究饮食中的胆固醇如何调节 肝脏和小肠中的高密度脂蛋白合成。一种单一的 兔apoA抗血清将用于定量检测 免疫共沉淀法从标记的肝细胞和标记的小细胞中提取apoA-1 肠粘膜细胞定位载脂蛋白A的主要部位- 1在正常和高胆固醇血症兔体内的合成 测定膳食胆固醇对载脂蛋白A比率的影响 1这些器官的合成。载脂蛋白A-1的相对速率 合成将以占总蛋白质的百分比来表示 合成的。这项研究有望为我们提供有用的 关于膳食的作用机制的生化信息 胆固醇调节高密度脂蛋白水平的降低和诱导 兔动脉粥样硬化的风险，可能还有人类的风险。我们的长期合作 目的是确定生物机制，通过 饮食中的胆固醇调节致动脉粥样硬化和 抗动脉粥样硬化血浆脂蛋白。

New Zealand White rabbits develop hypercholesterolemia, hyperlipoproteinemia, and atherosclerosis when fed a diet containing 1% (w/w) cholesterol for 4-8 weeks. A predominant characteristic of this cholesterol-induced hyperlipoproteinemia is the appearance of beta-very low density lipoprotein (beta-VLDL), an atherogenic plasma lipoprotein particle, which is rich in apoliprotein E (apoE) and cholesteryl esters (CE). There is also a dramatic reduction in high density lipoprotein (HDL) levels in the plasma of cholesterol-fed rabbits. HDL particles are anti- atherogenic and are rich in apolipoprotein A-1 (apoA-1) and CE. It is the aim of this research plan to provide a biochemical explanation for the disappearance of HDL particles in cholesterol- fed rabbits. Their disappearance may be due to a decrease in synthesis or to an increase in catabolism or to both. The HDL2 and HDL3 subfractions of the HDL fraction will be separated by polyacrylamide gel electrophoresis and by polyanion precipitation techniques. The gels will be scanned with a densitometer, and the HDL2 and HDL3 peak areas for normal and cholesterolemic rabbits will be compared. In addition, the cholesterol and apoA-1 content of these two HDL subclasses will be measured with an enzymatic assay will determine which of these two HDL subclasses is declining in the cholesterol-fed rabbit. They will also determine if apoA- 1 and cholesterol are disappearing from one or both of these particles at equal rates. Since apoA-1 and cholesterol are disappearing from one or both of these particles at equal rates. Since apoA-1 is the major apolipoprotein in the HDL fraction, its regulation by dietary cholesterol will be used as a model of how dietary cholesterol are disappearing from one or both of these particles at equal rates. Since apoA-1 is the major apolipoprotein in the HDL fraction, its regulation by dietary cholesterol will be used as a model of how dietary cholesterol regulates the rate of HDL synthesis in the liver and small intestine. A monospecific antisera for rabbit apoA-will be used to quantitatively immunoprecipate apoA-1 from labeled hepatocytes and labeled small intestine mucosal cells in order to locate the major site of apoA- 1 synthesis in normal and cholesterolemic rabbits as well as to determine the effect of dietary cholesterol on the rates of apoA- 1 synthesis in these organs. The relative rates of apoA-1 synthesis will be expressed as the percent of total protein synthesized. This research is expected to provide useful biochemical information about the mechanisms by which dietary cholesterol regulates the reduction in HDL levels and the induction of atherosclerosis in rabbits and possibly in man. Our long-term objectives are to determine the biological mechanisms by which dietary cholesterol regulates the metabolism of atherogenic and anti-atherogenic plasma lipoproteins.