Age-dependency of alpha- and beta-adrenoceptors on thrombocytes and lymphocytes of asthmatic and nonasthmatic children |
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Authors: | D. Reinhardt T. Zehmisch B. Becker M. Nagel-Hiemke |
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Affiliation: | (1) Children's Hospital, University of Düsseldorf, Moorenstraße 5, D-4000 Düsseldorf, Federal Republic of Germany |
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Abstract: | Among the possible mechanisms which may cause wheezing or asthmatic episodes a genetically determined -adrenoceptor blockade and a hyperresponsiveness of -andrenoceptors has been postulated. Evidence to support this hypothesis stems from an increased bronchial sensitivity to -blockers, a reduced formation of cyclic AMP in response to -adrenergic stimulation and enhanced -adrenergic responses in asthmatic subjects. The recent development of techniques for measuring the specific, high-affinity binding of radiolabeled -and -adrenergic antagonists made it possible to study - and -adrenoceptors in vitro. Based upon the assumption that a change in the number and/or affinity of adrenergic receptors might be a general phenomenon, we have performed - and -receptor binding studies on lymphocytes and platelets from wheezing infants and asthmatic children as well as of infants, children, and adults not suffering from these diseases.Using 125[I]-cyanopindolol (ICYP) and 3[H]-yohimbine (HYOH) as highly specific ligands for - and -adrenoceptors, the following results were obtained: (1) Lymphocytes and platelets from control subjects and asthamatics bound similar amounts of ICYP and HYOH and thus showed no differences either in the number or the affinity of - and -adrenoceptors. Lymphocytes and platelets of wheezing and nonwheezing infants also bound the same amounts of the radioligands. (2) In asthmatic children receiving 4×2 puffs salbutamol -adrenoceptor were down-regulated and this may mimic -adrenoceptor blockade. (3) When subjects were divided into four categories according to age (0–5, 5–10, 10–20 years, adults) the number of -adrenoceptor binding sites showed an age-dependent increase. The number and affinity of -adreneceptor binding sites on platelets was neither influenced by age nor disease.It is concluded that the - and -adrenoceptors of wheezing infants and asthmatic children at least on blood cells are normal. However the -adrenoceptors show an age-dependent maturation process, which may account for an unresponsiveness to -adrenoceptor agonists in wheezing infants.Supported by a grant from the Ministerium für Wissenschaft und Forschung, NRWPresented at the 19th Workshop for Pediatric Research, University of Göttingen, March 10–11, 1983 |
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Keywords: | Bronchial asthama Adrenergic theory /content/k44172t815j156n7/xxlarge945.gif" alt=" agr" align=" BASELINE" BORDER=" 0" >- and /content/k44172t815j156n7/xxlarge946.gif" alt=" beta" align=" MIDDLE" BORDER=" 0" >-adrenoceptors Blood cells Age-dependent maturation |
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