Effect of Na-K adenosinetriphosphatase activity on relaxation of canine tracheal smooth muscle.
The effect of Na-K adenosinetriphosphatase (ATPase) on relaxation induced by isoproterenol, prostaglandin E2, sodium nitroprusside, and forskolin, a specific stimulant of adenylate cyclase, was investigated in canine tracheal smooth muscle strips. Relaxation in response to isoproterenol, prostaglandin E2, and forskolin was significantly decreased after inhibition of the Na-K ATPase by ouabain or a potassium-free medium, but relaxation to sodium nitroprusside was not affected. Relaxation to isoproterenol was greater in muscles contracted by 5-hydroxytryptamine than in those contracted by acetylcholine. The stimulation of Na-K ATPase activity with potassium also caused differences in relaxation between tissues contracted with 5-hydroxytryptamine or acetylcholine. Relaxation caused by isoproterenol by activation of the Na-K-ATPase was also decreased by the Ca2+-channel antagonists, verapamil and diltiazem. The results suggest 1) Na-K ATPase activity modulates relaxation caused by isoproterenol, prostaglandin E2, and forskolin in canine tracheal smooth muscle, 2) isoproterenol or activation of the Na-K ATPase may cause relaxation partly by reducing Ca2+ influx through potential-dependent Ca2+ channels, and 3) the differences in the inhibitory effects of isoproterenol and Na-K ATPase activity on muscles contracted by acetylcholine and 5-hydroxytryptamine could be due to differences between these contractile agents in their dependence on extracellular Ca2+ for activation.
Gunst
S J
SJ
Department of Physiology and Biophysics, Mayo Clinic, Rochester, Minnesota.
Stropp
J Q
JQ
D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology; D005576:Colforsin / Q000494:pharmacology; D015232:Dinoprostone; D004285:Dogs; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects*; D009126:Muscle Relaxation / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects / Q000201:enzymology*; D009599:Nitroprusside / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D011458:Prostaglandins E / Q000494:pharmacology; D000254:Sodium-Potassium-Exchanging ATPase / Q000037:antagonists & inhibitors / Q000502:physiology*; D014132:Trachea / Q000187:drug effects / Q000201:enzymology*
D002121:Calcium Channel Blockers; D011458:Prostaglandins E; D009599:Nitroprusside; D005576:Colforsin; D000254:Sodium-Potassium-Exchanging ATPase; D015232:Dinoprostone; D007545:Isoproterenol; D011188:Potassium