The identification of apparently novel cyclic AMP and cyclic GMP phosphodiesterase activities in guinea‐pig tracheal smooth muscle
Open Access
- 1 September 1994
- journal article
- Published by Wiley in British Journal of Pharmacology
- Vol. 113 (1) , 3-4
- https://doi.org/10.1111/j.1476-5381.1994.tb16164.x
Abstract
Phosphodiesterase (PDE) activities that were capable of hydrolysing cyclic AMP (Km = 6.8 ± 2 μm) and cyclic GMP (Km = 6.7 ± 1.6 μm) 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 μm and 45 ± 14 μm 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.Keywords
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