Brucato F H, Pizzo S V
Department of Pathology, Duke University Medical Center, Durham, NC 27710.
Blood. 1990 Jul 1;76(1):73-9.
The catabolism of streptokinase (SK) and polyethylene glycol derivatives of SK (PEG-SK) were studied in mice. The clearance and catabolism of SK:plasmin (SK:Pm) and PEG-SK:Pm activator complexes were also investigated. Native 125I-SK cleared rapidly (t1/2 = 15 minutes) from the circulation, with the majority of the ligand accumulating in the liver and gastrointestinal (GI) tract and a substantial fraction also localizing in the kidneys. SK, which was removed from the plasma by the liver, was secreted into bile and then the GI tract. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) demonstrated that 125I-SK recovered from liver and bile was homogeneous and of the same molecular weight (mol wt approximately 50,200) as native SK. PEG-125I-SK cleared slowly (t1/2 greater than 200 minutes), with more than 80% of the preparation localizing in liver and GI tract. The PEG-125I-SK secreted into the bile was also intact. The bile containing 125I-SK was incubated with stoichiometric amounts of plasminogen and electrophoresed under nondenaturing conditions. This study demonstrated that the secreted SK was able to form SK:Pg complexes. SDS-PAGE also showed activation of 125I-Pg that was incubated with recovered bile containing the SK. 125I-SK:Pm catabolism was also studied. In these experiments, the mol wt approximately 42,000 fragment obtained when SK is cleaved by plasmin was found in the bile. This fragment of 125I-SK was not recovered as part of a complex with plasmin, consistent with our previous observations that catabolism of SK:Pm involves transfer of the plasmin to plasma proteinase inhibitors while SK is catabolized independently. By contrast, when PEG-125I-SK:Pm was injected into mice, only intact PEG-125I-SK was found in the bile, consistent with our previous observations that the PEG derivatization blocks its degradation by plasmin.
在小鼠体内研究了链激酶（SK）及其聚乙二醇衍生物（PEG - SK）的分解代谢。还研究了SK：纤溶酶（SK：Pm）和PEG - SK：Pm激活剂复合物的清除和分解代谢。天然的125I - SK从循环系统中快速清除（半衰期 = 15分钟），大部分配体积聚在肝脏和胃肠道（GI），还有相当一部分定位于肾脏。被肝脏从血浆中清除的SK分泌到胆汁中，然后进入胃肠道。十二烷基硫酸钠聚丙烯酰胺凝胶电泳（SDS - PAGE）表明，从肝脏和胆汁中回收的125I - SK是均一的，并且与天然SK具有相同的分子量（约50,200道尔顿）。PEG - 125I - SK清除缓慢（半衰期大于200分钟），超过80%的制剂定位于肝脏和胃肠道。分泌到胆汁中的PEG - 125I - SK也是完整的。将含有125I - SK的胆汁与化学计量的纤溶酶原一起孵育，并在非变性条件下进行电泳。该研究表明，分泌的SK能够形成SK：Pg复合物。SDS - PAGE还显示，与含有SK的回收胆汁一起孵育的125I - Pg被激活。还研究了125I - SK：Pm的分解代谢。在这些实验中，在胆汁中发现了SK被纤溶酶切割时获得的分子量约为42,000的片段。125I - SK的这个片段没有作为与纤溶酶的复合物的一部分被回收，这与我们之前的观察结果一致，即SK：Pm的分解代谢涉及纤溶酶转移到血浆蛋白酶抑制剂，而SK是独立分解代谢的。相比之下，当将PEG - 125I - SK：Pm注射到小鼠体内时，在胆汁中仅发现完整的PEG - 125I - SK，这与我们之前的观察结果一致，即PEG衍生化阻止了其被纤溶酶降解。
