Activation of cyclic AMP-dependent protein kinase during canine lower esophageal sphincter relaxation.
In isolated strips of opossum lower esophageal sphincter (LES) smooth muscle, elevation of cyclic AMP (cAMP) content is associated with relaxation. Because the activation state of cyclic nucleotide-dependent protein kinases may be a more sensitive measure of functionally important changes in cyclic nucleotide levels, we examined the ability of several pharmacological agents and electrical stimulation of the enteric neurons to activate cAMP dependent-protein kinase (cA-PK) and to relax isolated strips of LES smooth muscle. Addition of either isoproterenol or SK&F 94120, a selective inhibitor of the low Km cAMP phosphodiesterase to isolated strips of canine LES produced concentration-dependent increases in the activity ratio of cA-PK and concentration-dependent relaxations of canine LES. In contrast, although both zaprinast (M&B 22948), a selective inhibitor of the cyclic GMP selective phosphodiesterase, and sodium nitroprusside relaxed canine LES neither drug significantly increased the activity ratio of cA-PK. Furthermore, electrical stimulation of the enteric neurons produced a frequency-dependent relaxation but did not significantly activate cA-PK. To eliminate the possibility that the rapid metabolism of cAMP prevented us from observing a significant activation of cA-PK during electrical field stimulation, the ability of electrical field stimulation (1.0 Hz) to activate cA-PK was examined in the presence of 0.1 mM 3-isobutyl-1-methylxanthine. At at concentration of 0.1 mM, 3-isobutyl-1-methylxanthine, by itself, significantly increased the activity ratio of cA-PK; however, there was no additional activation produced by electrical field stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)
Barnette
M S
MS
Department of Pharmacology, Smith Kline Beecham p.l.c., King of Prussia, Pennsylvania.
Grous
M
M
Torphy
T J
TJ
Ormsbee
H S
HS
D015105:3',5'-Cyclic-AMP Phosphodiesterases / Q000037:antagonists & inhibitors; D000818:Animals; D002316:Cardiotonic Agents / Q000494:pharmacology; D004285:Dogs; D004558:Electric Stimulation; D004789:Enzyme Activation / Q000187:drug effects; D004943:Esophagogastric Junction / Q000187:drug effects / Q000201:enzymology*; D005260:Female; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D009126:Muscle Relaxation / Q000187:drug effects*; D011494:Protein Kinases / Q000378:metabolism*; D011688:Purinones / Q000494:pharmacology; D011719:Pyrazines / Q000494:pharmacology
D002316:Cardiotonic Agents; D011688:Purinones; D011719:Pyrazines; C048350:5-(4-acetamidophenyl)pyrazin-2(1H)-one; D011494:Protein Kinases; D015105:3',5'-Cyclic-AMP Phosphodiesterases; C011145:zaprinast; D007545:Isoproterenol