Distribution Of Ghrelin-positive Cells In The Gastrointestinal Tract And Associated Gene Expression In Meihua And Landrace Piglets

Ghrelin is a gastric endocrine hormone of various biological functions, including the regulation of appetite, promotion of the secretions of growth hormone and gastric acid. Ghrelin displayedits biological functions mainly through its functional receptor GHSR-1a.Ghrelin is mainly secreted by the stomach, and the number of ghrelin-positive cells and its level were affected by many factors including the development, environment(diet) and microbial infection, and so on, affecting the growth of the piglets.Meihua pigs, a famous native breedof Guangdong Province, Ghina,displaying the characteristic oflow lean ratio and slow growth, gradually eliminated by the market, is facing the crisis of extinction. Landrace pig,however, is characterized byhigh lean meat and fast growth, is widely popular in the pig industry.In order to explore the characteristics of Ghrelin cells and secretory activity in the Meihua and Landrace pigs, we analyzed the Ghrelin-positive cells and its expression in different parts of the gastrointestinal tractin Meihua and Landrace piglets.A total of 16 piglets weaned at 30 days of age were randomly selected in this experiment, with 8 Meihua and 8 Landrace piglets respectively; they wereraised under the same conditions and fed the same diet, until 65 days of age.Then serum samples were collected before slaughter, followed by collection of the gastrointestinal samples. The Ghrelin-positive cells in the gastrointestinal tractwere identified and countedby immunohistochemistry and immunofluorescence. ELISAwas used to determine theghrelin levels in gastrointestinal tissue and serum. The m RNA gene expression of GHRL, GHSR and GHSR-1a in the gastrointestinal mucosa was determined byquantitative real-time PCR. The resultswereas follows:(1) The immunohistochemistry and immunofluorescence analyses demonstrated that both open- and closed-type Ghrelin-positive cells were detected in the gastric glands, pylorus, duodenum and jejunum of Meihua and Landrace piglets.(2)The density of Ghrelin-positive cells in pylorusof the Landrace piglets was significantly higher than that of the Meihua piglets.The density of Ghrelin-positive cellsin jejunum was the opposite. The density ofthe closed-type as well as the open-type Ghrelin-positive cellsin jejunum of the Meihua piglets was significantly higher than that of the Landrace piglets. The density ofthe open-type Ghrelin-positive cellsin pylorusand duodenum of the Landrace piglets was significantly higher than that of the Meihua piglets.(3) The density of Ghrelin-positive cells of Meihua and landrace piglets is similar with declining numbers along the gastrointestinal tract.(4)The ratio of open- to closed-type Ghrelin-positive cellsin the gastricglands, pylorus, duodenum and jejunumof Meihuawas 9:1, 6:1, 4:1 and3:1,respectively.While the ratio of open- to closed-type Ghrelin-positive cellsin the gastricglands, pylorus, duodenum and jejunumof Landrace pigletswas 9:1, 7:3, 2:1 and 7:2,respectively.(5) The ghrelin levels in gastricglands, of Landrace piglets were significantly higher than those of the Meihua piglets. The ghrelin levels in serum, duodenum and jejunum of the Meihua piglets were significantly higher than those of the Landrace piglets.(6)The m RNA gene expression of GHRL in the gastricglands of Landrace piglets was significantly higher than those of the Meihua piglets.The m RNA gene expression of Meihua and Landrace piglets is consistent, as Ghrelin cell number distribution trend, is along the direction of the intestinal tract.(7) The m RNA gene expression of GHSR in the gastricglands, pylorusand jejunum of Landrace piglets were significantly higher than those of the Meihua piglets. The m RNA gene expression of GHSR-1a in the jejunum of Meihua piglets was significantly higher than that of the Landrace piglets.