The Expression And Binding Property Of Melatonin Receptor In Adult Hepatoma Tissues

OBJECTIVE To determin whether there existed melatonin receptor (MR) (included its subtypes: melatonin receptor 1, MT1 and melatonin receptor 2, MT2) in adult hepatoma tissues and its adjacent tissues, and know the signification of the differences expression in the human hepatocellular carcinoma and its adjacent tissues. The study was also to investigate the role of Mel in cancer and the mechanism of anti-tumor. METHODS Immunohistochemistry was used to detect the subtypes MT1, MT2 of MR and identify its subcellular distribution. The adult hepatoma tissues and its adjacent tissues were detected the mRNA of MR with PT-PCR. Specific binding and kinetic analyses of melatonin receptor were measured by radioligand binding assay.RESULTS(1) The characteristic of the MR expression in human hepatoma tissues and its adjacent tissuesThe results of immunohistochemistry showed that significance in-Strong MT1 and MT2 receptor subtypes expression that had brown granules deposited in membrane, cytosol and nucleus of the hepatoma cells was observed in group hepatoma tissues than group its adjacent tissues, but the expression of them principally localized in the membrane and cytosol, expressed in the nucleus at least. (2) The difference expression of mRNA in adult hepatoma tissues and its adjacent tissuesThe mRNA of MR fragment of the expected size in adult hepatoma tissues and its adjacent were determined by RT-PCR. The mRNA of MT1 and MT2 melatonin recep tor subtype were expressed in all groups, but in adult hepatoma had a higher quantity than that in its adjacent tissues(p<0.05).(3) The specific binding and kinetic analyses of melatonin receptor in adult hepatoma tissues and its adjacent tissuesSpecific binding and kinetic analyses of melatonin receptor were measured by radioligand binding assay. By Scatchard analysis, The maximum binding capacity (Bmax) of 125I-Mel specific binding of adult hepatoma tissues and its adjacent tissues was 0.29±0.07pmol·g-1 and 1.16±0.28pmol·g-1(p<0.05), Equilibrium dissociation constant (Kd)48.7±6.5 pmol·L-1 and 26.5±4.6pmol·L-1(P>0.05). The trait of MR, saturation and reversibility, was detected by 125I-Mel specific binding kinetic analyses.CONCLUSIONS1. The first found that MR existed in the adult hepatoma tissues, including the two subtypes of MT1 and MT2.2. The first found that the obvious difference expression of MR and its mRNA in adult hepatoma tissues and its adjacent tissues.3. MR characters of the specific binding sites were low binding capacity,high affinity,saturation and reversibility.