Chow Edwin C Y, Liu Lichuan, Ship Noam, Kluger Ronald H, Pang K Sandy
Department of Pharmaceutical Sciences, University of Toronto, Toronto, ON, Canada M5S 3M2.
Drug Metab Dispos. 2008 May;36(5):937-45. doi: 10.1124/dmd.107.019174. Epub 2008 Feb 14.
The role of haptoglobin in liver cell entry of acellular native hemoglobin, and cross-linked human hemoglobin, a potentially useful oxygen-carrier alternative in transfusion medicine, was examined in the recirculating, perfused rat liver preparation. Doses of tritiated native human or beta-chain [trimesoyl-(Lys82)beta-(Lys82)beta] cross-linked human hemoglobin were preincubated with haptoglobin-containing rat plasma or Krebs Henseleit bicarbonate buffer for 30 min and used for perfusion. Concentrations (dpm/ml) in reservoir, before and after separation of the hemoglobins and metabolites by gel filtration fast protein liquid chromatography column chromatography, were similar, showing mostly the presence of intact hemoglobin. Each hemoglobin species underwent a rapid distribution phase, followed by a protracted elimination phase. The radioactivity in bile at 3 h consisted of low molecular weight metabolites, and cumulative excretion was slightly higher when rat plasma was present: for native hemoglobin, 7.1 +/- 1.6% versus 9.2 +/- 2.1% dose; for cross-linked hemoglobin, 5.0 +/- 1.7% versus 7.2 +/- 0.8% dose. Data fit to a two-compartment model and physiologically based model revealed a significantly faster influx clearance (CL(influx)) over the metabolic intrinsic clearance (CL(int, met)). The ratios of CL(influx)/CL(int, met) were 125 and 535 for native hemoglobin in the absence and presence of rat haptoglobin, respectively, according to compartmental analyses; the ratios were 25 and 53, respectively, according to physiological modeling. The corresponding ratios for cross-linked hemoglobin in the absence and presence of rat haptoglobin were 55 and 81, respectively, and 24 and 70 for compartmental and physiological modeling. Although haptoglobin enhanced the hepatic internalization of the hemoglobins, the impact on the net clearance was lessened since degradation was the rate-limiting step.
在再循环灌注大鼠肝脏制备模型中，研究了触珠蛋白在无细胞天然血红蛋白和交联人血红蛋白进入肝细胞过程中的作用。交联人血红蛋白是输血医学中一种潜在有用的氧载体替代品。将一定剂量的氚标记天然人血红蛋白或β链[三甲基甲硅烷基-(Lys82)β-(Lys82)β]交联人血红蛋白与含触珠蛋白的大鼠血浆或 Krebs Henseleit 碳酸氢盐缓冲液预孵育 30 分钟后用于灌注。通过凝胶过滤快速蛋白质液相色谱柱色谱法分离血红蛋白和代谢产物前后，储液器中的浓度（dpm/ml）相似，表明大部分存在完整的血红蛋白。每种血红蛋白都经历了快速分布阶段，随后是持久的消除阶段。3 小时时胆汁中的放射性由低分子量代谢产物组成，当存在大鼠血浆时，累积排泄量略高：对于天然血红蛋白，分别为剂量的 7.1±1.6%和 9.2±2.1%；对于交联血红蛋白，分别为剂量的 5.0±1.7%和 7.2±0.8%。数据拟合到二室模型和基于生理学的模型显示，流入清除率（CL(influx)）明显快于代谢内在清除率（CL(int, met)）。根据房室分析，在不存在和存在大鼠触珠蛋白的情况下，天然血红蛋白的 CL(influx)/CL(int, met) 比值分别为 125 和 535；根据生理学建模，该比值分别为 25 和 53。在不存在和存在大鼠触珠蛋白的情况下，交联血红蛋白的相应比值分别为 55 和 81，房室和生理学建模的比值分别为 24 和 70。尽管触珠蛋白增强了血红蛋白的肝脏内化，但由于降解是限速步骤，对净清除率的影响有所减轻。
