Internalization of Recombinant Tissue-Type Plasminogen Activator by Isolated Rat Hepatocytes is via Coated Pits
| Autor: | Gary J Marks, Kei-Lai L Fong, Sylvia T. Hoffstein, Timothy K. Hart, Glenn F. Rush, Peter J. Bugelski |
|---|---|
| Rok vydání: | 1990 |
| Předmět: |
Nigericin
media_common.quotation_subject Acridine orange Coated Pit Hematology Biology Tissue plasminogen activator Molecular biology chemistry.chemical_compound medicine.anatomical_structure chemistry Biochemistry Hepatocyte medicine Receptor Internalization Plasminogen activator medicine.drug media_common |
| Zdroj: | Thrombosis and Haemostasis. 63:251-258 |
| ISSN: | 2567-689X 0340-6245 |
| DOI: | 10.1055/s-0038-1645204 |
| Popis: | SummaryThe uptake and internalization of tissue-type plasminogen activator (t-PA) by freshly isolated rat hepatocytes was investigated. Electron microscopic examination of the uptake of t-PA-colloidal gold conjugates (t-PA-gold) by isolated rat hepatocytes showed that t-PA-gold was internalized via coated pits. This was inhibited with excess t-PA. Uptake of 125I-t-PA by isolated rat hepatocytes was a rapid, saturable, and specific process. The initial rate of specific uptake was 0.1 fmol/106 cells per min. The specific uptake plateaued at 1.4 fmol/106 cells by 30 min and declined to 0.8 fmol/106 cells at 2 h. Depletion of cellular ATP by 85-90% did not affect the initial rate of specific uptake. However, specific uptake by ATP-depleted hepatocytes at 30 min was reduced by 37%. By 2 h specific uptake by ATP-depleted hepatocytes was only 5% lower than by untreated hepatocytes, suggesting that processing of t-PA and/or its receptor is ATP-dependent. Uptake of 125I-t-PA was temperature dependent. Specific uptake was reduced by ∼20% at 22° C and by 70% at temperatures below 16° C. Finally, inhibition of coated pit formation by K+-depletion with nigericin decreased the uptake of 125I-t-PA. This inhibition was shown to be K+-specific since treatment with nigericin in the presence of K+ did not inhibit coated pit formation or 125I-t-PA uptake. A threshold K+-depletion level for inhibition of coated pit formation was also demonstrated since treatment under conditions that reduced cellular K+ by only 54% had no effect on coated pit formation or 125I-t-PA uptake. These data support our hypothesis that internalization of t-PA by isolated rat hepatocytes is via coated pits and suggest that uptake of t-PA is a receptor-mediated process. |
| Databáze: | OpenAIRE |
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