Kloppel T M
Veterans Administration Medical Center, Denver, Colorado.
J Cell Physiol. 1989 Mar;138(3):555-60. doi: 10.1002/jcp.1041380316.
We have utilized the in situ perfused rat liver under nonrecirculating conditions to examine the effect of temperature on the metabolism and biliary secretion of [125I]-asialoorosomucid (ASOR). In this manner we were able to follow the fate of a single round of internalized ligand. In control livers perfused at 37 degrees C, approximately 50% of [125I]-ASOR injected into the portal vein was extracted on first pass. Five minutes after the injection, radioactivity, which had been extracted initially, began to appear in the hepatic venous effluent. Within 25 min, 50% of the initially extracted radioactivity was released into the perfusion medium; the bulk of this radioactivity (greater than 95%) was soluble in trichloroacetic acid. In livers perfused at temperatures slightly less than 37 degrees C (30-35 degrees C), first-pass extraction of [125I]-ASOR was similar to that observed at 37 degrees C. However, a severalfold decrease in the rate of release of radioactivity from the liver into the perfusion medium was noted at the lower perfusion temperatures; whereas greater than 50% of the initially extracted radioactivity was released within 30 min from livers perfused at 37 degrees C, only 5% was released at 30 degrees C. At the lower perfusion temperature, a larger proportion of the released radioactivity was acid precipitable (24% vs. 5%). Some radioactivity also was recovered in the bile; of the total amount of radioactivity released from the liver in 30 min at 37 degrees C, approximately 5% was directed into the bile. At lower temperatures of perfusion, a greater fraction of the radioactivity that was released from the liver was directed into the bile (20% at 30 degrees C vs. 5% at 37 degrees C). The data imply that the endosomal pathway to the lysosome is highly sensitive to slight reductions in temperature while the transcytotic route into bile is less sensitive. Lower temperatures might prolong the residence time of ASOR in the prelysosomal endosomal compartments, and thereby increase the likelihood that undegraded ligand will be returned to the blood or be missorted into bile.
我们利用非循环条件下原位灌注的大鼠肝脏，来研究温度对[125I] - 去唾液酸糖蛋白（ASOR）代谢及胆汁分泌的影响。通过这种方式，我们能够追踪单轮内化配体的去向。在37℃灌注的对照肝脏中，注入门静脉的[125I] - ASOR在首次通过时约50%被摄取。注射后5分钟，最初摄取的放射性开始出现在肝静脉流出物中。25分钟内，最初摄取的放射性的50%释放到灌注培养基中；这些放射性的大部分（超过95%）可溶于三氯乙酸。在略低于37℃（30 - 35℃）的温度下灌注的肝脏中，[125I] - ASOR的首次通过摄取与在37℃时观察到的相似。然而，在较低的灌注温度下，从肝脏释放到灌注培养基中的放射性速率下降了几倍；在37℃灌注的肝脏中，超过50%的最初摄取的放射性在30分钟内释放，而在30℃时仅释放5%。在较低的灌注温度下，释放的放射性中较大比例是酸沉淀性的（24%对5%）。一些放射性也在胆汁中回收；在37℃下30分钟内从肝脏释放的总放射性中，约5%进入胆汁。在较低的灌注温度下，从肝脏释放的放射性中更大比例进入胆汁（30℃时为20%，37℃时为5%）。数据表明，通向溶酶体的内体途径对温度的轻微降低高度敏感，而进入胆汁的转胞吞途径则不太敏感。较低的温度可能会延长ASOR在前溶酶体内体区室中的停留时间，从而增加未降解配体返回血液或被错误分选到胆汁中的可能性。
