ABSTRACT
Aim To determine whether there existed melatonin receptor (MR) in adult hepatoma tissue and to observe its property of binding.Methods Immuno-histochemistry 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 (B_(max)) was (0.29±0.07) pmol·g~(-1) protein. Equilibrium dissociation constant (K_d) was (48.7±6.5) pmol·L~(-1). The trait of MR, saturation and reversibility, was detected by ~(125)I-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.