The effect of methacholine and histamine on cyclic AMP-dependent protein kinase activity in the guinea-pig isolated trachea.
The effects of methacholine and histamine were examined on cyclic AMP-dependent protein kinase (A-kinase) activity in guinea-pig isolated trachea, using kemptide as a substrate for phosphorylation during the determination of the enzyme activity. Methacholine (EC90, 10 microM) induced a rapid reduction in the basal A-kinase activity ratio, which was maximal after 30 s. This initial reduction coincided with the early phase of isometric tension development, and returned to control levels 4 min after the addition of methacholine. Pretreatment with atropine inhibited the methacholine response. In contrast, histamine (EC90, 30 microM) was without effect upon A-kinase activity ratio. The results establish the sensitivity of the A-kinase assay using kemptide and demonstrate that not all contractile agonists have the capacity to inhibit basal activity of A-kinase in airway smooth muscle.
Langlands
J M
JM
Department of Physiology and Pharmacology, University of Strathclyde, Glasgow, Scotland.
Rodger
I W
IW
D000818:Animals; D006168:Guinea Pigs; D006632:Histamine / Q000494:pharmacology*; D066298:In Vitro Techniques; D007537:Isometric Contraction / Q000187:drug effects; D008297:Male; D008688:Methacholine Compounds / Q000494:pharmacology*; D009130:Muscle, Smooth / Q000187:drug effects / Q000201:enzymology; D011494:Protein Kinases / Q000378:metabolism*; D014132:Trachea / Q000187:drug effects / Q000201:enzymology*
D008688:Methacholine Compounds; D006632:Histamine; D011494:Protein Kinases