Investigation on New Material for DDS : Study on the Mechanisms of Release of Mucopolysaccharide from Liver in Rats

(1)低分子量水fh （7000DA）的Michaelis常数Km比高分子量水fh （20000Da）的Michaelis常数Km大5倍，但其他参数与高分子量水fh相当。因此，Km的增加，或表观亲和力的降低，以及在大范围摄取中分子量的降低，可能是报道的低分子量肝素肝摄取降低的原因。(2)分离肝素与大鼠Kupffer细胞的关联具有浓度依赖性，解离常数为3.4 nM，最大关联容量为1.3 pmol/10^6个细胞，表明其参与了一个特殊的机制。这也表明摄取机制可能不同于受体介导的多肽内吞作用，而可能是由清道夫受体介导的。(3)通过测定低分子量分离肝素（LMWFH: 7000Da）和高分子量分离肝素（HMWFH: 16000Da）的蛋白结合，评价分离肝素与血浆蛋白相互作用的分子量依赖性。在α -球蛋白和白蛋白存在的情况下，LMWFH的结合分数分别为0.5和0.8，是HMWFH的10倍左右，分别为0.04和0.1，表明随着分子量的降低，结合程度降低。然而，虽然这些蛋白对低分子量低腰氢的摄取的减少程度与低分子量低腰氢的结合部分相似，但对低分子量低腰氢的摄取的减少程度远小于结合部分。(4)分离肝素（HMWFH: 23000Da）与Kupffer细胞的平衡结合呈浓度依赖性，解离常数为5.7 nM，最大结合量为1.5 pmol/10^6个细胞。几种清道夫受体配体竞争性地抑制了分离肝素与库普弗细胞的结合，也抑制了肝素的内化，提示清道夫受体参与了分离肝素的摄取。清道夫受体介导的摄取被认为是不依赖于atp的，不同于多肽的受体介导的吸附内吞和吞噬作用，尽管它在温度依赖性上表现出受体介导的内吞的典型特征。少

(1) The Michaelis constant, Km for the extended uptake of LMWFH (7000DA) was 5 times larger than that of 21 nM for HMWFH (20000Da), but the other parameters were comparable with those for HMWFH.Therefore, an incease in Km, or a decease in apparent affinity, with a decrease in molecular weight in the extended uptake may be responsible for the reportde lower hepatic uptake of low molecular weight hepanin.(2) The association of fractionated heparin with rat Kupffer cells was concentration-dependent with a dissociation constant of 3.4 nM and a maximum association capacity of 1.3 pmol/10^6 cells, suggesting the involvement of a specialized mechanism. It is also suggested that the uptake mechanism may differ from receptor-mediated endocytosis of polypeptides and be mediated by scavenger receptors.(3) Molecular weight dependency in the interaction of fractionated haparin with plasma proteins was evaluated by determining the protein binding of low molecular weight fractionated heparin (LMWFH : … More 7000Da) and high molecular weight fractionated heparin (HMWFH : 16000Da). The bound fraction of LMWFH were 0.5 and 0.8 in the presence of alpha-globulin and albumin, respectively, and were about 10 times larger than those HMWFH,0.04 and 0.1, suggesting a reduction in binding with a decrease in molecular weight. However, While the uptake of LMWFH was reduced by these porteins by extents of similar to bound fractions of LMWFH,the uptake of HMWFH was reduced by extents fare smaller than bound fractions.(4) The equilibrium binding of fractionated heparin (HMWFH : 23000Da) to Kupffer cells was concentration-dependent with the dissociation constant of 5.7 nM and the maximun binding capacity of 1.5 pmol/10^6 cells. Several ligands of scavenger receptors inhibited the binding of fractionated heparin to Kupffer cells competitively and also the intemalization of heparin, suggesting the involvement of scavenger receptors in the uptake of fractionated heparin. The scavenger receptor-mediated uptake is suggested to be ATP-independent and different from receptor-mediated and adsorptive endocytosis of polypeptides and phagocytosis, although for temperature dependency ti showed the typical characteristics of receptor-mediated endocytosis. Less