Huang J, Sloop C H, Roheim P S, Wong L
Department of Physiology, Louisiana State University Medical Center, New Orleans.
Arteriosclerosis. 1990 Sep-Oct;10(5):720-6. doi: 10.1161/01.atv.10.5.720.
We studied the interstitial fluid concentration of two lipid-metabolizing enzymes (lipoprotein lipase and hepatic triacylglycerol lipase) to determine their importance in interstitial modification of filtered lipoproteins. Despite the use of a very sensitive lipase assay (1 nmol of fatty acid release/ml/hr), lipase activities in plasma and in peripheral and skeletal muscle lymph from control dogs were below the sensitivity of our assay. After heparin injection, hepatic triacylglycerol lipase and lipoprotein lipase activities in plasma were similar. However, the postheparin hepatic triacylglycerol lipase activities in peripheral and skeletal muscle lymph were only 1.4% and 1.1%, respectively, those of plasma. This concentration is considerably less than the lymph concentration of albumin, which has a similar size to the lipases but has a lymph concentration of 30% to 40% of plasma. Lipoprotein lipase activity in peripheral lymph and skeletal muscle lymph was 2.7% and 4.8%, respectively, of plasma activity. Since lipoprotein lipase has a similar size as hepatic triacylglycerol lipase, the disproportionate amount of lipoprotein lipase in lymph as compared to hepatic triacylglycerol lipase could be due to heparin crossing the capillary endothelium and displacing lipoprotein lipase from peripheral cells. Injection of radioactive heparin confirmed that it does cross into the interstitial space in sufficient concentrations to displace lipase from peripheral cells. We conclude that most of the lipase found in lymph after heparin injection is derived from peripheral cells and not from plasma. Furthermore, hepatic triacylglycerol lipase does not play a role in high density lipoprotein remodeling in interstitial fluid. Therefore, it seems likely that the considerable remodeling of high density lipoprotein that we found previously results from its interaction with peripheral cells.
我们研究了两种脂质代谢酶（脂蛋白脂肪酶和肝甘油三酯脂肪酶）的组织液浓度，以确定它们在滤过脂蛋白的组织间隙修饰中的重要性。尽管使用了非常灵敏的脂肪酶测定法（每毫升每小时释放1纳摩尔脂肪酸），但对照犬血浆以及外周和骨骼肌淋巴中的脂肪酶活性低于我们测定法的灵敏度。注射肝素后，血浆中的肝甘油三酯脂肪酶和脂蛋白脂肪酶活性相似。然而，肝素注射后外周和骨骼肌淋巴中的肝甘油三酯脂肪酶活性分别仅为血浆活性的1.4%和1.1%。该浓度远低于白蛋白的淋巴浓度，白蛋白与脂肪酶大小相似，但其淋巴浓度为血浆的30%至40%。外周淋巴和骨骼肌淋巴中的脂蛋白脂肪酶活性分别为血浆活性的2.7%和4.8%。由于脂蛋白脂肪酶与肝甘油三酯脂肪酶大小相似，与肝甘油三酯脂肪酶相比，淋巴中脂蛋白脂肪酶数量不成比例可能是由于肝素穿过毛细血管内皮并将脂蛋白脂肪酶从外周细胞中置换出来。注射放射性肝素证实它确实以足够的浓度进入组织间隙，从而将脂肪酶从外周细胞中置换出来。我们得出结论，肝素注射后在淋巴中发现的大多数脂肪酶源自外周细胞而非血浆。此外，肝甘油三酯脂肪酶在组织液中高密度脂蛋白重塑过程中不起作用。因此，我们之前发现的高密度脂蛋白的大量重塑似乎是其与外周细胞相互作用的结果。
