Ca(2+)-dependent and Ca(2+)-permeable ion channels in aortic endothelial cells.
We investigated whether osmotic stress would activate specific ion channels in bovine aortic endothelial cells (BAECs). In isotonic medium (290 mosmol/kgH2O), cell-attached patch recordings contained both 165-pS K+ channels activated by depolarization and 40-pS K+ channels activated by 200 nM bradykinin. These inwardly rectifying K+ channels were activated by raising "cytoplasmic" Ca2+ in inside-out patches. BAEC exposed to hypotonic bath (220 mosmol/kg) exhibited a 20% decrease in intracellular K+ content within 5 min. Cell-attached patches revealed biphasic K+ channel activation with hypotonic exposure; initial activation of 165- and 40-pS K+ channels (1-3 min) was followed by a delayed but sustained reactivation of both K+ channels (> 5 min). The delayed reactivation phase was dependent on the presence of external Ca2+ and was attenuated by 10 microM gadolinium. A 28-pS nonselective cation channel (NSCC), which conducted inward Ca2+ current, was also detected during hypotonic exposure. This NSCC was stimulated by hyperpolarization and was blocked by 10 microM gadolinium. In BAEC 1) hypotonic exposure activates Ca(2+)-dependent, 165- and 40-pS K+ channels biphasically; 2) the initial phase is independent of external Ca2+, while the delayed phase requires external Ca2+; and 3) Ca(2+)-permeable, 28-pS NSCCs stimulated by membrane hyperpolarization provide a pathway for external Ca2+ influx.
D000818:Animals; D001011:Aorta / Q000166:cytology / Q000378:metabolism*; D001920:Bradykinin / Q000494:pharmacology; D002118:Calcium / Q000493:pharmacokinetics / Q000494:pharmacology*; D002417:Cattle; D002478:Cells, Cultured; D004594:Electrophysiology; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism*; D007038:Hypotonic Solutions / Q000494:pharmacology; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism*; D010539:Permeability; D011188:Potassium / Q000378:metabolism; D015221:Potassium Channels / Q000187:drug effects / Q000378:metabolism / Q000502:physiology
D007038:Hypotonic Solutions; D007473:Ion Channels; D015221:Potassium Channels; D011188:Potassium; D001920:Bradykinin; D002118:Calcium