Effects of histamine and endothelin-1 on membrane potentials and ion currents in bovine tracheal smooth-muscle cells.
We tested the effects of tetraethylammonium (TEA), acetylcholine (ACh), histamine, and endothelin-1 on single airway smooth-muscle cells from bovine trachea, using the patch-clamp technique. Resting membrane potential was -48 +/- 1 mV (n = 47). Both TEA and ACh significantly depolarized the membrane, by +28 +/- 4 mV (P < 0.001, n = 12) and +21 +/- 2 mV (P < 0.01, n = 7), respectively, in the whole-cell configuration. In contrast, both histamine and endothelin-1 hyperpolarized the membrane, by -21 +/- 6 mV (P < 0.01, n = 8) and -15 +/- 2 mV (P < 0.01, n = 8), respectively. Calcium-dependent large-conductance K+-channels (127 pS) and small-conductance K+ channels (21 pS) were identified in excised patches. The small-conductance K+ channel was inhibited by 4-aminopyridine and activated by both histamine and endothelin-1. Furthermore, TEA did not alter the membrane hyperpolarization by these agonists, suggesting that the small-conductance K+ channel or delayed-rectifier K+ channel was involved in the membrane hyperpolarization. Membrane hyperpolarization by histamine and endothelin-1 suggests that activation of voltage-dependent calcium channels (VDCCs) or of calcium influx does not contribute substantially to the contractile response of airway smooth-muscle contraction to these agonists.
Nara
M
M
First Department of Internal Medicine, Tohoku University School of Medicine, Sendai, Japan.
Sasaki
T
T
Shimura
S
S
Oshiro
T
T
Irokawa
T
T
Kakuta
Y
Y
Shirato
K
K
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D002417:Cattle; D002478:Cells, Cultured; D018679:Cholinergic Agonists / Q000494:pharmacology; D004594:Electrophysiology; D019332:Endothelin-1 / Q000494:pharmacology*; D006632:Histamine / Q000494:pharmacology*; D007473:Ion Channels / Q000187:drug effects*; D008564:Membrane Potentials / Q000187:drug effects*; D016210:Methacholine Chloride / Q000494:pharmacology; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D018408:Patch-Clamp Techniques; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology; D014132:Trachea / Q000187:drug effects*
D018679:Cholinergic Agonists; D019332:Endothelin-1; D007473:Ion Channels; D000644:Quaternary Ammonium Compounds; D016210:Methacholine Chloride; D006632:Histamine; C027917:tetramethylammonium; D000109:Acetylcholine