Nocturnal asthma. Beta 2-adrenoceptors on peripheral mononuclear leukocytes, cAMP- and cortisol-plasma concentrations
To evaluate pathophysiologic mechanisms of the predominantly nocturnal complaints in atopic bronchial asthma, the expression and function of beta 2-adrenoceptors on peripheral mononuclear leukocytes (pMNL), the cAMP--as well as the cortisol--plasma concentrations were studied in eight healthy men an...
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Veröffentlicht in: | Chest 1991-11, Vol.100 (5), p.1239-1245 |
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Zusammenfassung: | To evaluate pathophysiologic mechanisms of the predominantly nocturnal complaints in atopic bronchial asthma, the expression
and function of beta 2-adrenoceptors on peripheral mononuclear leukocytes (pMNL), the cAMP--as well as the cortisol--plasma
concentrations were studied in eight healthy men and ten so far untreated male asthmatic patients at 4-h intervals for 24
h. No difference was seen in the beta 2-adrenoceptor density (Bmax) on pMNL between healthy and asthmatic men (24-h means
+/- SE: 908 +/- 59 sites per cell and 821 +/- 54 sites per cell, respectively). The equilibrium dissociation constant (Kd),
however, was significantly higher in the asthmatic patients (24-h mean +/- SE: 8.8 +/- 1.2 pmol/L vs 3.0 +/- 0.2 pmol/L in
healthy men, p less than 0.0001), which is equivalent to a lower affinity of the beta 2-adrenoceptors for the radioligand
125iodocyanopindolol. Bmax showed a statistically significant circadian variation, but Kd did not. The circadian variation
in Bmax was reflected in the basal intracellular cyclic adenosine-monophosphate (cAMP) content of the cells investigated.
High Kd values (equivalent to low receptor affinities) tended to be associated with small increases of the intracellular cAMP
content after in vitro stimulation by 10(-7) mol/L isoprenaline (isoproterenol) (24-h mean +/- SE: 1.4 +/- 0.2 pmol/10(6)
cells; r = -0.529, p = 0.05 at r = -0.549, n = 10). Plasma cAMP concentrations were found to be significantly lower in the
asthmatic patients (24-h means +/- SE: 22.9 +/- 1.3 nmol/L vs 29.1 +/- 1.1 nmol/L, p less than 0.0001). Plasma cortisol concentrations
were significantly higher in the asthmatic patients (24-h means +/- SE: 0.500 +/- 0.084 mumol/L vs 0.319 +/- 0.063 mumol/L).
The results support the hypothesis that a lesion of the beta-adrenergic system contributes to the pathophysiology of atopic
bronchial asthma. In the patients investigated in this study, such a lesion could be demonstrated in the affinity rather than
in the number of beta 2-adrenoceptors expressed on peripheral cells of the immune system (pMNL). According to present-day
knowledge of adrenergic effects on pMNL, such an affinity decrease of beta 2-adrenoceptors could account for overshooting
immune responses. In association with other factors influencing respiratory function, it could be responsible for the predominantly
nocturnal complaints in atopic bronchial asthma. Plasma cortisol concentrations did not appear to be related to the principal
cause of " |
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ISSN: | 0012-3692 1931-3543 |
DOI: | 10.1378/chest.100.5.1239 |