Study on Pharmacokinetics of Bioactive Macromolecular Drug for DDS : Scavenger Receptor-Mediated Internarization and Release of Fractionated [^3H] Heparin

(1)观察大鼠Kupffer细胞、原代培养肝实质细胞和腹腔巨噬细胞对高分子量分离肝素（20,000Da）的浓度依赖性摄取。库普弗细胞和腹腔巨噬细胞的解离常数和K_d相差不大，分别为5.7 nM和6.7 nM，而肝实质细胞的解离常数和K_d远低于53.5nM。Kupffer细胞和腹腔巨噬细胞的最大结合容量B_<max>分别为1.5和1.9 pmol/10^6细胞，而肝实质细胞的最大结合容量B_<max>为32.8 pmol/10^6细胞。因此，与库普弗细胞和腹膜巨噬细胞相比，肝实质细胞具有更大的结合能力和更低的对分离肝素的亲和力。(2)原代培养的Kupffer细胞和肝实质细胞的解离常数K_d随着分离肝素分子量的减小而增大，但两种细胞的最大结合容量B_<max>基本保持不变。(3)初始化分馏[^3H]肝素的表观释放常数K_<rel, app>为初始化表观释放常数K_<int, app>的1 / 3，且当温度从37 C降至4 C时，表观释放常数降低。(4)分馏[^3H]肝素的表观释放常数K_<rel, app>由0.074增加到0.127h^<-1>，分馏[^3H]肝素的分馏量由0.259增加到5.764 pmol/mg protein。另一方面，在培养液中加入α -球蛋白、氯喹和莫能菌素对表观释放常数没有影响。

(1)The concentration-dependent uptake of high molecular weight fractionated heparin (20,000Da) was observed with rat Kupffer cells, liver parenchymal cells in primary culture and peritoneal macrophages. The dissociation constants, K_d for Kupffer cells and peritoneal macrophages were similar to each other showing 5.7 and 6.7 nM,respectively whereas the value for liver parenchymal cells was much lower than those showing 53.5nM.The maximum binding capacity, B_<max> were 1.5 and 1.9 pmol/10^6 cells, respectively for Kupffer cells and peritoneal macrophages, whereas liver parenchymal cells took much larger value of 32.8 pmol/10^6 cells. Thus, the liver parenchymal cells were demonstrated to have larger binding capacity and less affinity to the fractionated heparin comparing to Kupffer cells and peritoneal macrophages..(2)The dissociation constants, K_d for both Kupffer cells and liver parenchymal cells in primary culture increased with decrease of molecular weight of fractionated heparin, although the maximum binding capacity, B_<max> for both kind of cells remained almost unchanged.(3)The apparent release constant for intemalized fractionated [^3H] heparin, K_<rel, app> was one-third of the value for the apparent intemalization constant K_<int, app> and decreased when the temperature was lowered from 37ﾟC to 4ﾟC.(4)The apparent release constant for intemalized fractionated [^3H] heparin, K_<rel, app> increased from 0.074 to 0.127h^<-1>, when the intemalized amount of fractionated [^3H] heparin was raised from 0.259 to 5.764 pmol/mg protein. On the other hand, the apparent released constant was not influenced by addition of alpha-globulin, chloroquine or monensin to the incubation medium.