Variations of the circadian rhythm of cAMP in bronchial asthma after administration of fenoterol.

In the study of the physiology and therapeutic response of bronchial asthma the evaluation of adrenergic activity is of fundamental importance. References in the literature indicate a reduction of the intracellular concentration of cyclic AMP in asthmatic patients, as well as a reduction in the response to beta-adrenergic stimulants. This work intends to expose the possible effects of the prolonged administration of beta-stimulants (as employed in bronchial asthma therapy) on the levels of circulating cyclic nucleotides. From another perspective, we wish to relate the clinical improvement after beta-adrenergic therapy and the levels of cyclic AMP. Ten patients suffering from bronchial asthma were selected for the study, and cyclic AMP levels were determined at different hours during the day (in order to evaluate its circadian rhythm), before and after treatment with 5 mg of Fenoterol (beta-stimulant), three times a day during 20 days. The results showed a statistically significant (p less than 0.002) reduction in the levels of cyclic AMP in the asthmatics. An increase in circulating cyclic AMP was observed after treatment, remaining high throughout the day, and differing from pre-treatment levels by 4.9 p.Moles after 9 hours to 2 p.Moles 13 hours after initiation of treatment. Prolonged administration of Fenoterol modifies the circadian rhythm of cyclic AMP, causing an increase in its circulating levels. The magnitude of this increase is of less amplitude than the one observed after the administration of a single dose of Fenoterol and immediate determination.