Nocturnal and early morning wheezing is very common in patients with bronchial asthma, but the mechanism has not been clear yet. Therefore, we investigated the circadian changes of cyclic AMP, cyclic GMP, catecholamine, histamine and serotonin in plasma sampled from inpatients with bronchial asthma and from normal subjects as a control. The level of plasma cyclic AMP was highest at 4: 00 p. m. and lowest at 4: 00 a. m. (
P<0.005) in control group whereas the level of plasma cyclic AMP was highest at 12: 00 noon and lowest at 4: 00 p. m. in patients with bronchial asthma. The level of plasma histamine was significantly higher (
P<0.001) in asthmatics than normal subjects at midnight. The level of plasma cyclic GMP and serotonin were higher in asthmatics than normal subjects, but that of plasma norepinephrine and dopamine were lower in asthmatics than normal subjects. Plasma epinephrine level in asthmatics was highest at 4: 00 p. m. and lowest at 4: 00 a. m. (
P<0.05). Our study suggests that nocturnal asthma may be, at least in part, caused by a circadian fall in plasma epinephrine and release of histamine and thereby results in bronchoconstriction.
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