Lally J I, Barter P J
J Lab Clin Med. 1979 Apr;93(4):570-82.
The in vivo metabolism of esterified cholesterol in plasma HDL has been studied in rabbits injected with preparations of HDL which had been labeled with 3H in the esterified and free cholesterol moieties. These labeled HDL preparations had been isolated either from the serum of donor rabbits which had been previously injected with 3H-mevalonic acid or from rabbit serum which had been incubated in vitro at 37 degrees with 3H-cholesterol. In terms of subsequent in vivo metabolism, there were no significant differences between the in vivo labeled and in vitro labeled HDL preparations. It was also found that the presence of free 3H-cholesterol in the injected HDL had very little effect on the recipient esterified 3H-cholesterol results. The removal of esterified 3H-cholesterol from the recipient HDL fraction was biphasic, with the initial phase largely reflecting a transfer into the plasma VLDL and LDL fractions rather than a removal from the plasma compartment. In fact, the initial rate of removal from HDL was very much influenced by the distribution of esterified cholesterol mass in the different lipoprotein fractions; the greater the proportion in VLDL and LDL, the more rapid was the initial rate of removal from HDL. A transfer of esterified cholesterol from HDL to VLDL and LDL was estimated to be of the order of 150 to 200 mumol/L of plasma per hour, a value much greater than the reported rate of production of esterified cholesterol in rabbit plasma. The implication that such transfers might therefore have been partially reversible was confirmed in in vitro incubations of labeled HDL and unlabeled rabbit serum.
已在注射了经酯化胆固醇部分和游离胆固醇部分用³H标记的高密度脂蛋白（HDL）制剂的兔子中，研究了血浆HDL中酯化胆固醇的体内代谢情况。这些标记的HDL制剂要么是从先前注射了³H-甲羟戊酸的供体兔子血清中分离得到的，要么是从在37℃下与³H-胆固醇进行体外孵育的兔血清中分离得到的。就随后的体内代谢而言，体内标记的和体外标记的HDL制剂之间没有显著差异。还发现，注射的HDL中游离³H-胆固醇的存在对受体酯化³H-胆固醇的结果影响很小。受体HDL部分中酯化³H-胆固醇的去除是双相的，初始阶段主要反映了向血浆极低密度脂蛋白（VLDL）和低密度脂蛋白（LDL）部分的转移，而不是从血浆区室中去除。实际上，HDL中初始去除速率受不同脂蛋白部分中酯化胆固醇质量分布的影响很大；VLDL和LDL中所占比例越大，HDL中初始去除速率就越快。估计酯化胆固醇从HDL向VLDL和LDL的转移速率约为每小时每升血浆150至200μmol，该值远大于报道的兔血浆中酯化胆固醇的生成速率。在标记的HDL与未标记的兔血清的体外孵育中证实了这种转移可能部分是可逆的这一推断。
