Evidence that the anti-spasmogenic effect of the beta-adrenoceptor agonist, isoprenaline, on guinea-pig trachealis is not mediated by cyclic AMP-dependent protein kinase

Br J Pharmacol. 2001 Aug;133(8):1201-12. doi: 10.1038/sj.bjp.0704213.


1. The spasmolytic and anti-spasmogenic activity of beta-adrenoceptor agonists on airways smooth muscle is thought to involve activation of the cyclic AMP/cyclic AMP-dependent protein kinase (PKA) cascade. Here we have tested the hypothesis that PKA mediates the anti-spasmogenic activity of isoprenaline and other cyclic AMP-elevating agents in guinea-pig isolated trachea by utilizing a number of cell permeant cyclic AMP analogues that act as competitive 'antagonists' of PKA. 2. Anion-exchange chromatography of guinea-pig tracheae resolved two peaks of PKA activity that corresponded to the type I ( approximately 5%) and type II ( approximately 93%) isoenzymes. 3. Pre-treatment of tracheae with zardaverine (30 microM), vasoactive intestinal peptide (VIP) (1 microM) and the non-selective activator of PKA, Sp-8-CPT-cAMPS (10 microM), produced a non-parallel rightwards shift in the concentration-response curves that described acetylcholine (ACh)-induced tension generation. The type II-selective PKA inhibitor, Rp-8-CPT-cAMPS (300 microM), abolished this effect. 4. Pre-treatment of tracheae with Sp-8-Br-PET-cGMPS (30 microM) produced a non-parallel rightwards shift of the concentration-response curves that described ACh-induced tension generation. The selective cyclic GMP-dependent protein kinase (PKG) inhibitor, Rp-8-pCPT-cGMPS (300 microM), abolished this effect. 5. Pre-treatment of tracheae with isoprenaline (1 microM) produced a 10 fold shift to the right of the ACh concentration-response curve by a mechanism that was unaffected by Rp-8-Br-cAMPS (300 microM, selective inhibitor of type I PKA), Rp-8-CPT-cAMPS (300 microM) and Rp-8-pCPT-cGMPS (300 microM). 6. We conclude that the anti-spasmogenic activity of Sp-8-CPT-cAMPS, zardaverine and VIP in guinea-pig trachea is attributable to activation of the cyclic AMP/PKA cascade whereas isoprenaline suppresses ACh-induced contractions by a mechanism(s) that is independent of PKA and PKG.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetylcholine / pharmacology
  • Adrenergic beta-Agonists / pharmacology*
  • Animals
  • Cyclic AMP / analogs & derivatives
  • Cyclic AMP / metabolism
  • Cyclic AMP / pharmacology
  • Cyclic AMP-Dependent Protein Kinase Type II
  • Cyclic AMP-Dependent Protein Kinases / antagonists & inhibitors
  • Cyclic AMP-Dependent Protein Kinases / metabolism*
  • Cyclic GMP / analogs & derivatives
  • Cyclic GMP / metabolism
  • Cyclic GMP / pharmacology
  • Cyclic GMP-Dependent Protein Kinases / antagonists & inhibitors
  • Cyclic GMP-Dependent Protein Kinases / metabolism
  • Guinea Pigs
  • Isoenzymes / antagonists & inhibitors
  • Isoenzymes / metabolism
  • Isoproterenol / pharmacology*
  • Muscle Contraction / drug effects
  • Muscle Tonus / drug effects
  • Muscle, Smooth / drug effects*
  • Muscle, Smooth / enzymology
  • Muscle, Smooth / metabolism
  • Pyridazines / pharmacology
  • Trachea / drug effects*
  • Trachea / enzymology
  • Trachea / metabolism


  • Adrenergic beta-Agonists
  • Isoenzymes
  • Pyridazines
  • Cyclic AMP
  • Cyclic AMP-Dependent Protein Kinase Type II
  • Cyclic AMP-Dependent Protein Kinases
  • Cyclic GMP-Dependent Protein Kinases
  • Cyclic GMP
  • Isoproterenol
  • Acetylcholine
  • zardaverine