Cooper A D, Yu P Y
J Lipid Res. 1978 Jul;19(5):635-43.
Chylomicron remnants are removed intact by isolated perfused rat livers and their lipid components are metabolized by the liver (Biochim. Biophys. Acta 488: 464, 1977). The present study provides quantitative information regarding these processes. When the lipoprotein concentration of the perfusate was constant, the removal of chylomicron remnants increases lineraly for 17 min. The rate of remnant removal was a hyperbolic function of the perfusate's remnant concentration. The removal rate had aV max of 28microgram cholesterol per g liver per min and an apparent Km of 64 microgram cholesterol per ml perfusate. Feeding the liver donors a diet containing 1% cholesterol or 4% cholesterol and 1% cholic acid failed to alter the hepatic removal rate. The cholesteryl ester removed from the remnants was hydrolyzed at a rate that was a small fraction of the removal rate (about 0.5% of removed cholesteryl ester per min). The rate of cholesteryl ester hydrolysis did not appear to approach saturation in the range studied. Studies of the lysosomal cholesteryl ester hydrolase suggested that this enzyme was not responsible for limiting the initial rate of hydrolysis, raising the possibility that the degradation rate is determined by the movement of the removed remnant to the site of hydrolysis.
乳糜微粒残粒可被分离灌注的大鼠肝脏完整清除，其脂质成分在肝脏中代谢（《生物化学与生物物理学报》488: 464, 1977）。本研究提供了关于这些过程的定量信息。当灌注液中脂蛋白浓度恒定时，乳糜微粒残粒的清除在17分钟内呈线性增加。残粒清除率是灌注液中残粒浓度的双曲线函数。清除率的Vmax为每克肝脏每分钟28微克胆固醇，表观Km为每毫升灌注液64微克胆固醇。给肝脏供体喂食含1%胆固醇或4%胆固醇及1%胆酸的饮食未能改变肝脏的清除率。从残粒中清除的胆固醇酯以一定速率水解，该速率仅为清除率的一小部分（每分钟约为清除的胆固醇酯的0.5%）。在所研究的范围内，胆固醇酯水解速率似乎未达到饱和。对溶酶体胆固醇酯水解酶的研究表明，该酶并非限制初始水解速率的原因，这增加了降解速率由被清除的残粒向水解部位移动所决定的可能性。
