title: On the role of calcium in the acute release of tissue-type plasminogen activator and von Willebrand factor from the rat perfused hindleg region.
abstract: The involvement of calcium in the release of tissue-type plasminogen activator (t-PA) and von Willebrand Factor (vWF) from vascular endothelial cells was studied ex vivo using a rat hindleg perfusion system. By adding either platelet-activating factor or bradykinin to the perfusing Tyrode solution, a rapid release of t-PA and vWF was induced. Extracellular calcium was required for the acute release of both glycoproteins as this release was totally abolished in the presence of EGTA. The calcium ionophore A-23187 induced (Ca-dependently) the release of both proteins, suggesting that Ca-influx was also sufficient to induce release. The absence of an effect of the calcium L-type channel blockers, verapamil and diltiazem, and of the calcium channel agonist BAY K-8644, suggested that endothelial voltage-operated calcium channels were not involved in release. Trifluoperazine, a calmodulin antagonist, significantly inhibited the induced release of t-PA and vWF, while the "intracellular calcium antagonist" TMB-8 had no effect. Lanthanum chloride (200 microM) inhibited the induced release of t-PA but not that of vWF. Our results suggest that Ca2+ influx is essential for the release of t-PA and vWF from the perfused rat hindleg.
authors.affiliation: Gaubius Laboratory TNO, Leiden, The Netherlands.
authors.forename: N
authors.initials: N
authors.lastname: Tranquille
authors.forename: J J
authors.initials: JJ
authors.lastname: Emeis
mesh_terms: D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000037:antagonists & inhibitors / Q000502:physiology*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002147:Calmodulin / Q000037:antagonists & inhibitors; D004730:Endothelium, Vascular / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D006614:Hindlimb; D008297:Male; D010477:Perfusion; D051381:Rats; D011919:Rats, Inbred Strains; D013053:Spectrophotometry; D010959:Tissue Plasminogen Activator / Q000097:blood*; D014841:von Willebrand Factor / Q000378:metabolism*
chemical_list: D002121:Calcium Channel Blockers; D002147:Calmodulin; D014841:von Willebrand Factor; D000001:Calcimycin; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D010959:Tissue Plasminogen Activator; D002118:Calcium