title: Catabolism of human tissue plasminogen activator in mice.
abstract: The catabolism of human tissue plasminogen activator (t-PA) was studied in mice. The clearance of t-PA labeled with iodine 125 was rapid (t1/2). The clearance of phenylmethylsulfonyl-125I-t-PA, which is active site-inhibited, was identical to the active enzyme. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) demonstrated that the vast majority of 125I-t-PA injected into the circulation was present as free enzyme and not in a complex with inhibitors. The clearance of 125I-t-PA was unaltered by large molar excesses of several ligands of known clearance specificities, including macroalbumin, asialoorosomucoid, and diisopropylphosphorylthrombin and was also not altered in the presence of a 1,000-fold molar excess of unlabeled t-PA. Organ distribution studies demonstrated that the early rapid clearance of 125I-t-PA occurred in hepatocytes, followed by a later renal phase of clearance. The clearance of 125I-urokinase (UK) also was studied and was very similar in all aspects to the clearance of 125I-t-PA. These results suggest that both t-PA and UK are cleared from the circulation by unique nonsaturable processes localized in the liver that are independent of the proteinase active site.
mesh_terms: D000418:Albumins / Q000494:pharmacology; D000818:Animals; D011232:Chemical Precipitation; D004591:Electrophoresis, Polyacrylamide Gel; D006207:Half-Life; D006801:Humans; D007531:Isoflurophate / Q000494:pharmacology; D007668:Kidney / Q000502:physiology; D051379:Mice; D010664:Phenylmethylsulfonyl Fluoride / Q000494:pharmacology; D010960:Plasminogen Activators / Q000378:metabolism*; D012967:Sodium Dodecyl Sulfate; D014018:Tissue Distribution; D014238:Trichloroacetic Acid / Q000494:pharmacology; D014568:Urokinase-Type Plasminogen Activator / Q000378:metabolism
chemical_list: D000418:Albumins; D007531:Isoflurophate; D012967:Sodium Dodecyl Sulfate; D010664:Phenylmethylsulfonyl Fluoride; D014238:Trichloroacetic Acid; D010960:Plasminogen Activators; D014568:Urokinase-Type Plasminogen Activator