Histamine induces K+, Ca2+, and Cl- currents in human vascular endothelial cells. Role of ionic currents in stimulation of nitric oxide biosynthesis.
The nature of the membrane currents mediating agonist-induced Ca2+ entry and enhanced nitric oxide (NO) production in endothelial cells is still unclear. Using both perforated-patch and conventional whole-cell clamp technique, we have studied the membrane response associated with histamine stimulation of human vascular endothelial cells. In perforated-patch experiments, the initial histamine (10 mumol/L)-induced current reversed close to the K+ equilibrium potential and was blocked by tetrabutylammonium ions (TBA, 10 mmol/L). In addition, a TBA-insensitive current that developed slowly in the presence of histamine was recorded. This delayed histamine-induced current reversed close to neutral potential and was inhibited by SK&F 96365 (25 mumol/L), a putative blocker of receptor-operated Ca2+ channels. Similar histamine effects were observed in conventional whole-cell experiments using pipette solutions with low Ca(2+)-buffering capacity. Strong buffering of intracellular free Ca2+ suppressed the initial, but not the delayed, current response. The delayed component of histamine-induced current was substantially inhibited by the Cl- channel blocker N-phenylanthranilic acid (NPA, 100 mumol/L), and an eightfold change in the Cl- gradient shifted the reversal potential of this current by 30 mV. In Cl(-)-free solutions, histamine induced an SK&F 96365-sensitive NPA-resistant current, which, according to reversal potential measurements in 20 mmol/L extracellular Ca2+, corresponded to a cation conductance with 13- to 25-fold selectivity for Ca2+ over K+. Both SK&F 96365 and TBA strongly suppressed histamine-induced rises in intracellular free Ca2+ and cellular cGMP levels, whereas NPA did not. Our results provide the first demonstration that three distinct ionic conductances contribute to the histamine-induced membrane response of endothelial cells. It is suggested that histamine induces a Cl- conductance that is apparently not involved in Ca2+ homeostasis and regulation of NO biosynthesis, while, in parallel, joint activation of a rapidly induced K+ permeability and a slowly developing cation permeability mediate Ca2+ entry and stimulation of endothelial NO production.
Groschner
K
K
Institut für Pharmakologie und Toxikologie, Karl-Franzens-Universität Graz, Austria.
Graier
W F
WF
Kukovetz
W R
WR
D002118:Calcium / Q000502:physiology*; D002478:Cells, Cultured; D002712:Chlorides / Q000502:physiology*; D004594:Electrophysiology; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects* / Q000502:physiology*; D006632:Histamine / Q000494:pharmacology*; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D007477:Ions; D009569:Nitric Oxide / Q000096:biosynthesis*; D011188:Potassium / Q000502:physiology*; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology; D062367:ortho-Aminobenzoates / Q000494:pharmacology
D002712:Chlorides; D007093:Imidazoles; D007477:Ions; D000644:Quaternary Ammonium Compounds; D062367:ortho-Aminobenzoates; D009569:Nitric Oxide; D006632:Histamine; C001209:fenamic acid; C009405:tetrabutylammonium; C063159:1-(2-(3-(4-methoxyphenyl)propoxy)-4-methoxyphenylethyl)-1H-imidazole; D011188:Potassium; D002118:Calcium