Pingoud V A, Peters F, Haas T D, Trautschold I
Biochim Biophys Acta. 1982 Feb 25;714(3):448-55. doi: 10.1016/0304-4165(82)90153-2.
The interaction of glucagon with specific receptors has been studied in isolated intact neonatal and adult rat hepatocytes. The hormone binding measured directly with 125I-labelled glucagon was saturable and reversible. The 125I-labelled glucagon binding was inhibited by unlabelled homologous hormone at concentrations ranging from 0.5 nM to 50 microM. Two different binding models were assumed to analyse the binding data by a nonlinear least-squares procedure: (I) a single class of independent sites and (II) two classes of independent sites. The comparison of the fitted theoretical curves reveals that both binding models are in fact compatible with these data. Adult hepatocytes have a considerably higher affinity for glucagon than neonatal hepatocytes; the binding capacity of neonatal liver cells from 1-7-days-old rats proved to be markedly reduced compared with the cells from adult rats. The glucagon-induced intracellular cyclic AMP production was measured at various hormone concentrations under conditions identical to those for the determination of extracellular hormone binding. The correlation of both parameters indicates a direct connection between receptor-occupancy and adenylate cyclase stimulation of both parameters indicates a direct connection between receptor-occupancy and adenylate cyclase stimulation. These results suggest that a decreased receptor concentration in neonatal hepatocytes is responsible for the decreased cyclic AMP production.
已在分离的完整新生大鼠和成年大鼠肝细胞中研究了胰高血糖素与特定受体的相互作用。用¹²⁵I标记的胰高血糖素直接测定的激素结合是可饱和且可逆的。未标记的同源激素在0.5 nM至50 μM的浓度范围内可抑制¹²⁵I标记的胰高血糖素结合。假定了两种不同的结合模型，通过非线性最小二乘法分析结合数据：（I）一类独立位点和（II）两类独立位点。拟合的理论曲线比较表明，这两种结合模型实际上都与这些数据相符。成年肝细胞对胰高血糖素的亲和力明显高于新生肝细胞；与成年大鼠的细胞相比，1至7日龄大鼠的新生肝细胞的结合能力明显降低。在与测定细胞外激素结合相同的条件下，在各种激素浓度下测量胰高血糖素诱导的细胞内环磷酸腺苷（cAMP）生成。这两个参数的相关性表明受体占据与腺苷酸环化酶刺激之间存在直接联系。这些结果表明，新生肝细胞中受体浓度降低是环磷酸腺苷生成减少的原因。
