The identification of apparently novel cyclic AMP and cyclic GMP phosphodiesterase activities in guinea-pig tracheal smooth muscle

F Burns, P A Stevens, N J Pyne

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Phosphodiesterase (PDE) activities that were capable of hydrolysing cyclic AMP (Km = 6.8 +/- 2 microM) and cyclic GMP (Km = 6.7 +/- 1.6 microM) were isolated from tracheal smooth muscle. These enzyme(s) activities were insensitive to stimulation by calcium/calmodulin and to inhibition by cyclic GMP, rolipram (type IV inhibitor) and siguazodan (type III inhibitor). Zaprinast was a relatively poor inhibitor of both cyclic AMP and cyclic GMP hydrolysis (IC50 = 46 +/- 9 microM and 45 +/- 14 microM respectively). These results suggest that tracheal smooth muscle may contain an apparently novel PDE. However, KCl (30 mM) which facilitates calcium entry in cells, depressed bradykinin-stimulated intracellular cyclic AMP formation, suggesting that the type I PDE may be functionally present. We suggest that considerable caution be exercised in identifying apparently novel PDE isoforms.
Original languageEnglish
Pages (from-to)3-4
Number of pages2
JournalBritish Journal of Pharmacology
Issue number1
Publication statusPublished - Sep 1994


  • 3',5'-cyclic-AMP phosphodiesterases
  • 3',5'-cyclic-GMP phosphodiesterases
  • animals
  • bradykinin
  • guinea pigs
  • isoenzymes
  • muscle, smooth
  • potassium chloride
  • trachea

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