Roan Y, Galant S P
Pediatr Res. 1982 Aug;16(8):591-3. doi: 10.1203/00006450-198208000-00001.
Using cord blood neutrophils (PMN) the maturity of the beta adrenergic receptor has been assessed. [3H]-Dihydroalprenolol isoproterenol-induced cyclic AMP generation to characterize receptor function. Data from six neonates and six adult controls revealed that neonatal PMN had significantly (P less than 0.001) fewer receptor sites (728 +/- 43 receptors/cell) compared to the adult (1302 +/- 68 receptors/cel); however, the affinity constants (Kd) were very similar (0.78 +/- 0.14 nM compared to 0.61 +!- 0.05 nM). Neonatal PMN also generated less isoproterenol-induced cyclic AMP than adult cells at all concentrations, reaching significance (P less than 0.005) at 10(-4) - 10(-6) M isoproterenol concentrations. No difference in the isoproterenol concentrations stimulating 50% of the maximal cyclic AMP generation (EC50) was found between the two populations. These data indicate that the neonatal PMN has decreased beta adrenergic receptor sites. No evidence of a receptor--adenylate cyclase coupling defect was detected. These findings could reflect ontogenic differences between the neonate and adult PMN. The effect of increased catecholamine secretion during the stress of delivery resulting in 'down regulation' of the beta adrenergic receptor cannot presently be ruled out.
利用脐血中性粒细胞（PMN）对β-肾上腺素能受体的成熟度进行了评估。使用[3H]-二氢阿普洛尔来表征异丙肾上腺素诱导的环磷酸腺苷（cAMP）生成以评估受体功能。来自6名新生儿和6名成人对照的数据显示，与成人（1302±68个受体/细胞）相比，新生儿PMN的受体位点显著减少（P＜0.001）（728±43个受体/细胞）；然而，亲和常数（Kd）非常相似（分别为0.78±0.14 nM和0.61±0.05 nM）。在所有浓度下，新生儿PMN产生的异丙肾上腺素诱导的cAMP也比成人细胞少，在异丙肾上腺素浓度为10^(-4) - 10^(-6) M时达到显著差异（P＜0.005）。在两个群体之间未发现刺激50%最大环磷酸腺苷生成（EC50）的异丙肾上腺素浓度有差异。这些数据表明新生儿PMN的β-肾上腺素能受体位点减少。未检测到受体 - 腺苷酸环化酶偶联缺陷的证据。这些发现可能反映了新生儿和成人PMN之间的个体发育差异。目前不能排除分娩应激期间儿茶酚胺分泌增加导致β-肾上腺素能受体“下调”的影响。
