Thrombin potentiates volume-activated chloride currents in pulmonary artery endothelial cells.
In bovine pulmonary artery endothelial cells, ionic currents and the concentration of free intracellular Ca2+ ([Ca2+]i) were measured with a combined patch clamp and Ca(2+)-fluorimetric method (Fura-2). Volume-activated Cl-currents (ICl,vol) were activated by a 13 or 28% decrease in tonicity. Thrombin, 1 U/ml, strongly potentiated ICl,vol preactivated by low hypotonicity (13% HTS) but had no effect on ICl,vol preactivated by stronger hypotonic challenges (28% HTS). The thrombin-induced potentiation was not affected by buffering [Ca2+]i at 50-100 nmol/l and omitting extracellular Ca2+. A peptide agonist of the thrombin receptor, SFLLRN, also potentiated ICl,vol, while an enzymatically inactive thrombin analogue, DIP-thrombin, was without effect. These result suggest that proteolytic activation of the thrombin receptor sensitises the activation of ICl,vol in endothelial cells in a Ca(2+)-independent mechanism.
Manolopoulos
G V
GV
Laboratorium voor Fysiologie, KU Leuven, Belgium.
Prenen
J
J
Droogmans
G
G
Nilius
B
B
D000818:Animals; D002417:Cattle; D018118:Chloride Channels / Q000187:drug effects / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D005456:Fluorescent Dyes; D016257:Fura-2; D007038:Hypotonic Solutions; D066298:In Vitro Techniques; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology; D008564:Membrane Potentials / Q000502:physiology; D018408:Patch-Clamp Techniques; D011651:Pulmonary Artery / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D018179:Receptors, Thrombin / Q000037:antagonists & inhibitors; D013917:Thrombin / Q000494:pharmacology*
D018118:Chloride Channels; D005456:Fluorescent Dyes; D007038:Hypotonic Solutions; D018179:Receptors, Thrombin; D013917:Thrombin; D016257:Fura-2