Expression Of GnRH-R And Its Regulation In Rat Hepacytes

Many studies have showed that gonadotropin-releasing hormone and its receptor exist in the organs and tissues of non-hypothalamus-pituitary axis, such as placental trophoblast cells, prostate, pancreas and some tumor tissues[1.2.3]. Chegini[4] first proved that the uterine smooth muscle cells exists the mRNA of GnRH and its receptor. Our previous studies had reported gastrointestinal pancreatic system can synthesize GnRH and the gastrointestinal pancreatic system[5] and thyroid gland were confirmed to contain GnRH-R positive cell[6.7]. GnRH is synthesized outside the hypothalamus-pituitary axis, and has its biological effects there. Gurrie[8]found that GnRH can significantly increase the [Ca2+] of placenta trophoblast cells, which participates the cell signal process. Tache[9] found that injection of GnRH analogues in ventricular and intravenous, the pH of gastric juice increased,its mechanism may be that GnRH analogues play the role indirectly by inhibiting the vagus nerve.In recent years many researchers have observed that the treatment dosage of GnRH analogues can lead to disorders of glucose metabolism, but the mechanism is not clear, may be related to the changes of sex hormone by using the GnRH analogues; whether there is a direct role in GnRH and glucose metabolism has no report. Liver is the main organ of metabolism, and there is GnRH in the gastrointestinal pancreatic system, so the question we pay attention is whether liver synthesize GnRH-R and whether GnRH influence the glucose metabolism via this receptor there.Methods:Rats liver sections were prepared. Immunohistochemistry SABC and in situ hybridization was used to observe GnRH-R in tissue sections of rat liver. The expression of GnRH-R in rat hepatocytes cultured with normal and high glucose concentrations was checked. At same time glycogen was stainned in PAS method.Results:(1) The hepatocytes of rat were found to be GnRH-R positive immunoreactivity and mRNA hybridization signal. Both immunohistochemical and in situ hybridization results showed that the positive material distributed in the cell membrane and cytoplasm, the nucleus was negative. The hepatocytes around the central vein in a liver lobule had more strong immunoreactivity of GnRH-R than the hepatocytes far away the central vein, as well as the hybridization signal of GnRH-R mRNA had same distribution character as immunohistochemical result. (2) Expression of GnRH-R in hepatocyte cultured in glucose concentrations of 1g/L and 2g/L was detected by SABC immunohistochemistry. The results were analyzed by the microscope analysis system and integrated optical density analysis software. It was found that the hepatocytes were cultured in normal glucose has the higher expression of GnRH-R than that in high glucose (P<0.01). Conclusions:(1) The hepatocytes of rat were found to be the GnRH-R immunoreactivity and have GnRH-R mRNA hybridization signals. It proves that rat liver can synthesize GnRH-R at the level of transcription and translation. Hepatocyte of different parts in liver lobules has different level of GnRH-R expression. The expression of GnRH-R increased near central veins. (2) Expression of GnRH-R in liver is affected by the glucose concentration, high glucose downregulation its expression.All these suggest GnRH produced from the gastrointestinal pancreatic system may participate in glucose metabolism via its receptor in liver.