Endothelin-1 is a potent activator of nonselective cation currents in human bronchial smooth muscle cells.
The effects of endothelin (ET)-1 on cultured human bronchial smooth muscle cells (HBSMC) were investigated and compared with those of histamine, using the patch clamp techniques and measurements of intracellular Ca(2+) ([Ca(2+)](i)). Both ET-1 and histamine caused an initial transient elevation of [Ca(2+)](i) by Ca(2+) mobilization, followed by a sustained rise due to Ca(2+) entry. Nicardipine inhibited the sustained phase, but La(3+) abolished it. With low ethyleneglycol-bis-(beta-aminoethyl ether)-N,N'-tetraacetic acid (EGTA) and K(+) internal solutions, both ET-1 and histamine induced a sustained depolarization from approximately -40 to -20 mV. Under voltage clamp conditions, both drugs transiently activated an outward K(+) current at a holding potential of 0 mV. Additionally, with a Cs(+) internal solution, they elicited another transient inward current, frequently followed by current oscillations. These transient currents were blocked by high EGTA or heparin. With high EGTA and Cs(+) internal solutions, both drugs activated a long-lasting inward current. The reversal potential of these agonist-induced currents was approximately 0 mV and was not altered by the replacement of internal or external concentration of Cl(-), suggesting that the inward current was a nonselective cation current (I(cat)). The half-maximal effective concentration to activate I(cat) was 12 nM for ET-1 and 11 microM for histamine. La(3+) and Cd(2+) abolished these agonist-induced I(cat). The effects of ET-1 on [Ca(2+)](i) and I(cat) could be blocked by combined pretreatment with BQ-123 and BQ-788. Sarafotoxin S6c also increased [Ca(2+)](i) and activated I(cat). By polymerase chain reaction of reverse transcribed RNA, we detected both ET-A and ET-B receptor messenger RNA. These results provide the first evidence that ET-1 is a potent activator of I(cat) in HBSMC via ET-A and ET-B receptors, and the activation of I(cat) plays an important role in ET-1-induced Ca(2+) entry in human airways.
Departments of Respiratory Medicine, Cardiovascular Medicine, and Gastroenterology, University of Tokyo, Graduate School of Medicine, Tokyo, Japan.
H
H
Oonuma
T
T
Nakajima
T
T
Nagata
K
K
Iwasawa
Y
Y
Wang
H
H
Hazama
Y
Y
Morita
K
K
Yamamoto
R
R
Nagai
M
M
Omata
D001980:Bronchi / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D002412:Cations / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D065128:Endothelin Receptor Antagonists; D019332:Endothelin-1 / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects; D006632:Histamine / Q000494:pharmacology; D006801:Humans; D007473:Ion Channels / Q000187:drug effects* / Q000502:physiology; D007811:Lanthanum / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects*; D009130:Muscle, Smooth / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D009529:Nicardipine / Q000494:pharmacology; D009842:Oligopeptides / Q000494:pharmacology; D010456:Peptides, Cyclic / Q000494:pharmacology; D010880:Piperidines / Q000494:pharmacology; D012333:RNA, Messenger / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D044022:Receptor, Endothelin A; D044023:Receptor, Endothelin B; D017466:Receptors, Endothelin / Q000235:genetics; D014757:Viper Venoms / Q000494:pharmacology
D002121:Calcium Channel Blockers; D002412:Cations; D065128:Endothelin Receptor Antagonists; D019332:Endothelin-1; D007473:Ion Channels; D009842:Oligopeptides; D010456:Peptides, Cyclic; D010880:Piperidines; D012333:RNA, Messenger; D044022:Receptor, Endothelin A; D044023:Receptor, Endothelin B; D017466:Receptors, Endothelin; D014757:Viper Venoms; C057354:sarafotoxins s6; C086539:BQ 788; D007811:Lanthanum; D006632:Histamine; D009529:Nicardipine; C072247:cyclo(Trp-Asp-Pro-Val-Leu); D002118:Calcium