[Contribution of K-channel and Na-K-ATPase to the relaxant responses of canine bronchial smooth muscle to various bronchodilators].
To determine whether activations of K-channel and Na-K-ATPase are involved in the action of bronchodilating agents, we studied the effects of various K-channel blockers and ouabain, a Na-K-ATPase inhibitor, on the relaxant responses of canine airway smooth muscle in vitro. Addition of charybdotoxin (ChTx), a Ca-activated potassium channel blocker, and ouabain had no effect on the responses to verapamil and BRL 38227, but inhibited those to salbutamol, forskolin, DBcAMP, and nitroprusside. Apamin, a low-conductance K-channel blocker, and glibenclamide, an ATP-sensitive K-channel blocker, had no effect on the smooth muscle relaxation induced by any agents. The inhibitory effect of ChTx was predominant when the concentration of bronchodilator was low, whereas the effect of ouabain was observed in the presence of a high concentration of bronchodilator. These results suggest that Ca-activated K-channel and Na-K-ATPase may participate in the relaxation induced by bronchodilators that can raise intracellular cyclic nucleotides, and that the contribution of each component differs under different concentrations of the drugs.
Tamaoki
J
J
First Department of Medicine, Tokyo Women's Medical College, Japan.
Tagaya
E
E
Chiyotani
A
A
Kanemura
T
T
Sakai
N
N
Yamauchi
F
F
Konno
K
K
D000818:Animals; D001980:Bronchi / Q000187:drug effects; D001993:Bronchodilator Agents / Q000494:pharmacology*; D000242:Cyclic AMP / Q000378:metabolism; D006152:Cyclic GMP / Q000378:metabolism; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D066298:In Vitro Techniques; D009126:Muscle Relaxation / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects*; D015221:Potassium Channels / Q000502:physiology*; D000254:Sodium-Potassium-Exchanging ATPase / Q000502:physiology*
D001993:Bronchodilator Agents; D015221:Potassium Channels; D000242:Cyclic AMP; D000254:Sodium-Potassium-Exchanging ATPase; D006152:Cyclic GMP