title: Calcium dependence of the thrombin-induced increase in endothelial albumin permeability.
abstract: We examined whether the increase in endothelial albumin permeability induced by alpha-thrombin is dependent on extracellular Ca2+ influx. Permeability of 125I-albumin across confluent monolayers of cultured bovine pulmonary artery endothelial cells was measured before and after the addition of 0.1 microM alpha-thrombin. In the presence of normal extracellular Ca2+ concentration ([Ca2+]o, 1000 microM), alpha-thrombin produced a 175 +/- 10% increase in 125I-albumin permeability. At lower [Ca2+]o (100, 10, 1, or less than 1 microM), alpha-thrombin caused a 140% increase in permeability (P less than 0.005). LaCl3 (1 mM), which competes for Ca2+ entry, blunted 38% of the increase in permeability. Preloading endothelial monolayers with quin2 to buffer cytosolic Ca2+ (Cai2+) produced a dose-dependent inhibition of the increase in 125I-albumin permeability. Preincubation with nifedipine or verapamil was ineffective in reducing the thrombin-induced permeability increase. A 60 mM K+ isosmotic solution did not alter base-line endothelial permeability. alpha-Thrombin increased [Ca2+]i in a dose-dependent manner and the 45Ca2+ influx rate. Extracellular medium containing 60 mM K+ did not increase 45Ca2+ influx, and nifedipine did not block the rise in 45Ca2+ influx caused by alpha-thrombin. Ca2+ flux into endothelial cells induced by alpha-thrombin does not occur through voltage-sensitive channels but may involve receptor-operated channels. In conclusion, the increase in endothelial albumin permeability caused by alpha-thrombin is dependent on Ca2+ influx and intracellular Ca2+ mobilization.
authors.affiliation: Departments of Physiology, Albany Medical College of Union University, New York 12008.
authors.forename: H
authors.initials: H
authors.lastname: Lum
authors.forename: P J
authors.initials: PJ
authors.lastname: Del Vecchio
authors.forename: A S
authors.initials: AS
authors.lastname: Schneider
authors.forename: M S
authors.initials: MS
authors.lastname: Goligorsky
authors.forename: A B
authors.initials: AB
authors.lastname: Malik
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology* / Q000502:physiology; D002417:Cattle; D002463:Cell Membrane Permeability / Q000187:drug effects*; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000187:drug effects / Q000502:physiology*; D007700:Kinetics; D009543:Nifedipine / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D011651:Pulmonary Artery; D012710:Serum Albumin, Bovine / Q000378:metabolism*; D013917:Thrombin / Q000502:physiology*; D014700:Verapamil / Q000494:pharmacology
chemical_list: D012710:Serum Albumin, Bovine; D014700:Verapamil; D013917:Thrombin; D009543:Nifedipine; D011188:Potassium; D002118:Calcium