Kee Patrick, Rye Kerry-Anne, Taylor John L, Barrett P Hugh R, Barter Philip J
University Department of Medicine, Royal Adelaide Hospital, Adelaide, Australia.
Arterioscler Thromb Vasc Biol. 2002 Nov 1;22(11):1912-7. doi: 10.1161/01.atv.0000038485.94020.7f.
Apolipoprotein (apo)A-I exists in 3 forms in plasma: as lipid-free apoA-I, as a component of pre-beta-migrating discoidal high density lipoproteins (HDLs), and as a component of alpha-migrating spherical HDLs. This study investigates (1) the in vivo metabolism of apoA-I in each of these forms and (2) the effects of hepatic lipase (HL) on apoA-I metabolism.
Wild-type and HL transgenic rabbits were studied. When lipid-free (125)I-apoA-I and 125I-apoA-I in pre-beta-migrating discoidal reconstituted HDLs (rHDLs) were injected into wild-type rabbits, the label rapidly appeared in alpha-migrating particles and decayed with the same fractional catabolic rate (FCR) as when they were injected as a component of spherical rHDLs. Spherical rHDLs did not change in size when they were injected into wild-type rabbits but were reduced in size in HL transgenic rabbits. The FCR of apoA-I in HL transgenic rabbits was double that in wild-type rabbits.
In vivo, (1) lipid-free apoA-I rapidly incorporates into preexisting alpha-migrating particles, (2) pre-beta-migrating discoidal HDLs are rapidly converted into alpha-migrating HDLs, (3) the FCR of apoA-I is independent of the form in which it is introduced into plasma, and (4) HL reduces the size of alpha-migrating HDLs and increases the rate of catabolism of apoA-I.
载脂蛋白（apo）A-I 在血浆中以 3 种形式存在：无脂 apoA-I、前β迁移盘状高密度脂蛋白（HDL）的组成成分以及α迁移球状 HDL 的组成成分。本研究调查了（1）每种形式的 apoA-I 在体内的代谢情况以及（2）肝脂酶（HL）对 apoA-I 代谢的影响。
对野生型和 HL 转基因兔进行了研究。将无脂的（125）I-apoA-I 和前β迁移盘状重组 HDL（rHDL）中的 125I-apoA-I 注射到野生型兔体内时，标记物迅速出现在α迁移颗粒中，并以与作为球状 rHDL 的组成成分注射时相同的分数分解代谢率（FCR）衰减。将球状 rHDL 注射到野生型兔体内时其大小不变，但在 HL 转基因兔体内其大小减小。HL 转基因兔中 apoA-I 的 FCR 是野生型兔的两倍。
在体内，（1）无脂 apoA-I 迅速掺入预先存在的α迁移颗粒中，（2）前β迁移盘状 HDL 迅速转化为α迁移 HDL，（3）apoA-I 的 FCR 与其引入血浆的形式无关，并且（4）HL 减小了α迁移 HDL 的大小并增加了 apoA-I 的分解代谢率。
