Ghrelin Gene Cloning And Its Expression Mechanism In’hypothalamus-Pituitary-Stomach’ Axis Of The Yak (Bos Grunniens)

In order to study adaptation mechanism of the yak under extreme long forage shortage and the alpine prairie feed environment as well as to further clarify regulatory mechanism of the alpine meadow ecosystem to be adapted by the plateau herbivores in Qinghai-Tibetan Plateau, this experiment is conducted. With gene cloning, immunohistochemistry and bioinformatics analysis software and other technologies and methods, yak Ghrelin gene cloning, contrast and analysis of gene sequence are carried out and to investigate regulation mechanism of the yak on starvation resistance in the hypothalamus-pituitary-stomach (HPS) axis by positioning and quantitative analysis.The results are as follows:(1) Part of Ghrelin gene sequence from yak is cloned firstly and the sequence length is475bp coding for159amine acids (gene sequence number: bankitl391517). The identities of the nucleotide sequence is95%for cattle. Analyzed as follows:Ghrelin gene of yak has four missing:5bp,13bp,281bp and282bp; six conversions:153bp:C→T,154bp:A→G,194bp: T→C,253bp:G→A,309bp:C→T，472bp:C→T and three transversions:340bp:C→G,441bp:G→C,473bp:T→G.(2) The sum area (S) and integrated optical density (IOD) of Ghrelin immunopositive productions of yak were much greater than the value of cattle in the same organization of HPS axis (P＜O.01).1) Ghrelin-like immunoreactive neurons was found in the arcuate nucleus (ARC), ventromedial nucleus (VMN), dorsomedial nucleus(DMN), the S and IOD of Ghrelin immunopositive productions in the hypothalamus nucleus were SARC＞SVMN＞SDMN and IODARC＞IODVMN＞IODDMN (P＞0.01).2) Ghrelin-positive cells mainly distributed in the anterior pituitary and not observed in the neurohypophysis and pituitary pars intermedia.3) Ghrelin immunopositive production was found in the gastric gland, cardiac gland and pyloric gland but not found in rumen, omasum and reticulum. Meanwhile, In different expression parts are different features, the S and IOD of Ghrelin immunopositive productions in the stomach were S Abomasum＞S Pyloric gland region＞S Cardiac gland region and IOD Abomasum＞IOD Pyloric gland region＞IOD Cardiac gland region (P＜0.01).Conclusion:The yak Ghrelin gene has high identity for cattle, and was very conservative. Ghrelin immunopositive productions was highly expressed in the arcuate nucleus, ventromedial nucleus and dorsomedial nucleus of the yak, the three nucleuses may play a major role in the regulation of feeding behavior, maintain the weight balance and energy metabolism. In the pituitary and stomach of the yak, Ghrelin may have important roles in appetite regulation and maintaining the energy metabolism by the way of autocrine and paracrine. In short, Ghrelin is highly expressed in the HPS axis of the yak, which is the important regulative mechanism of normal physiological process such as maintain the weight balance and energy metabolism in the harsh natural environment of the plateau.