[Lymphocytic beta-2-adrenergic receptor density and function in children].

To study the development of beta 2-adrenoceptor function during childhood we assessed beta 2-adrenoceptor density by (-)-125 iodocyanopindolol (ICYP) binding and responsiveness (cyclic AMP responses to 10 microM/l (-)-isoprenaline stimulation) in lymphocytes derived from 76 children aged 1 month to 18 years. The mean number of beta 2-adrenoceptors was 732 +/- 33 (231-1830) ICYP binding sites/cell: there was no difference between males and females. Calculation of the data of all children resulted in a significant positive correlation between lymphocyte beta 2-adrenoceptor density and age (p less than 0.05). This age-dependent increase in beta 2-adrenoceptor density was significantly correlated with the 10 microM/l (-)-isoprenaline-induced increase in the intracellular level of cyclic AMP (p less than 0.01), indicating that with age not only beta 2-adrenoceptor responsiveness increases. Infants below 2 years of age had a significant lower beta 2-adrenoceptor density (588 +/- 63 ICYP binding sites/cell; n = 8) when compared with the beta 2-adrenoceptor density in children older than 2 years (763 +/- 38 ICYP binding sites/cell; n = 68). This reduced beta 2-adrenoceptor density might be one of the reasons that treatment with beta-adrenoceptor sympathomimetic drugs is less effective at this age than in children of older age.