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Cyclic 3',5'-adenosine monophosphate and bronchial tone
European Journal of Pharmacology
|January 7, 1977
Summary
The cyclic adenosine monophosphate (cAMP) system plays a key role in relaxing bronchial smooth muscle. Studies show catecholamines increase cAMP formation, which is inhibited by propranolol, supporting this mechanism.
Area of Science:
- Pharmacology
- Biochemistry
- Physiology
Background:
- Adenylate cyclase and cAMP-phosphodiesterase activities in dog bronchus are comparable to other smooth muscle preparations.
- Catecholamines influence cAMP formation and bronchial smooth muscle relaxation.
Purpose of the Study:
- To investigate the role of the cyclic adenosine monophosphate (cAMP) system in mediating bronchial smooth muscle relaxation.
- To characterize the kinetic properties of bronchial cAMP-phosphodiesterase and the effects of various compounds.
Main Methods:
- Enzyme activity assays for adenylate cyclase and cAMP-phosphodiesterase.
- Measurement of cAMP formation in response to catecholamines.
- Assessment of bronchial smooth muscle relaxation in response to various agents.
- Kinetic analysis of cAMP-phosphodiesterase inhibition.
Main Results:
- Catecholamines (isoproterenol > epinephrine > norepinephrine) increased cAMP formation, an effect inhibited by propranolol.
- Bronchial cAMP-phosphodiesterase exhibited two distinct hydrolysis rates, with high-affinity inhibition by theophylline and papaverine.
- Theophylline and papaverine potencies for enzyme inhibition and smooth muscle relaxation were comparable.
- Dibutyryl cAMP demonstrated a relaxing effect on the bronchial strip.
Conclusions:
- The cAMP system is a significant biochemical mechanism involved in bronchial smooth muscle relaxation.
- The observed effects of catecholamines and inhibitors support the involvement of cAMP in bronchodilation.