成人肝癌组织褪黑素受体的表达和结合特性

The expression and binding property of melatonin receptor in adult hepatoma tissue

目的检测成人肝癌组织是否表达褪黑素受体(me-latonin receptor,MR),并探讨其结合特性。方法免疫组化法检测肝癌组织MR两种亚型(MT1、MT2)的表达和分布。采用放射配体结合法检测肝癌组织MR特异性结合和动力学特性。结果免疫组化结果显示,成人肝癌组织MT1和MT2均呈聚集型粽黄色颗粒阳性染色,主要分布在细胞膜和细胞质,细胞核中表达最少。放射配体结合结果表明,成人肝癌组织存有125I标记的褪黑素(125I-Mel)特异结合位点,最大结合容量(Bmax)值为(0.29±0.07)pmol.g-1 protein,平衡解离常数(Kd)值为(48.7±6.5)pmol·L-1,动力学分析表明该特异性结合特点为可饱和及可逆性结合。结论成人肝癌组织表达MR,包括MT1和MT2,其结合特性为低结合容量、高亲和力、可饱和性及可逆性。

Aim To determine whether there existed melatonin receptor （MR） in adult hepatoma tissue and to observe its property of binding. Methods Immunohistochemistry was used to detect MR and identify its subcellular distribution. Specific binding and kinetic analyses of melatonin receptor were measured by radioligand binding assay. Results The results of immunohistochemistry showed that MT1 and MT2 existed in membrane, cytosol and nucleus of the hepatoma cells, but the expression of them principally localized in the membrane and cytosol. The specific binding assay properties of MR were presented as follows： the maximum binding capacity （ Bmax ） was （ 0. 29 _＋ 0. 07 ） pmol · g^-1 protein. Equilibrium dissociation constant （ Kd） was （48.7 _＋ 6. 5） pmol · L^-1. The trait of MR, saturation and reversibility, was detected by ^125I-Mel specific binding kinetic analyses. Conclusions MR exists in adult hepatoma cells, furthermore, the subtypes of MR （MT1 and MT2） coexist in the membrane and cytosol, respectively, whose characters of the specific binding sites were low binding capacity, high affinity, saturation and reversibility.