Expression of gastric ghrelin and H+–K+-ATPase mRNA in weanling piglets and effect of ghrelin on H+–K+-ATPase expression and activity in gastric mucosal cells in vitro

This study was designed to investigate the effect of ghrelin on gastric acid secretion in weaning piglets both in vivo and in vitro. Thirty newborn piglets were selected from six litters and on 28, 35 (weaning), 38, 42 and 45 d of age, respectively, one piglet from each litter was killed and the mucosal tissue from gastric fundus was collected for detecting ghrelin mRNA as well as H+–K+-ATPase mRNA expression and activity. Primary cultures of gastric mucosal cells from 5-week-old weaning piglets were challenged with 3 × 10−5, 3 × 10−4, 3 × 10−3, 3 × 10−2 and 3 × 10−1 nmol/ml h-ghrelin, respectively, for 4 h in order to further clarify the effect of ghrelin on gastric H+–K+-ATPase mRNA expression and activity. Ghrelin mRNA expression in gastric fundus kept stable from 28 d to 42 d, followed by a sudden increase on 45 d, exhibiting a peak that was significantly higher than any other age groups investigated. H+–K+-ATPase activity and mRNA expression showed similar trends of increase with slightly different timing. H+–K+-ATPase mRNA expression tended to increase on 42 d, while H+–K+-ATPase activity started to rise from 35 d, but neither of them reached significantly higher levels until 45 d. In vitro, ghrelin significantly increased H+–K+-ATPase activity of gastric mucosal cells at 3 × 10−4, 3 × 10−3, and 3 × 10−2 nmol/ml, but augmented H+–K+-ATPase mRNA expression only at 3 × 10−4 nmol/ml. The results indicate that ghrelin mRNA expression is up-regulated 10 days after weaning in the gastric fundus of piglets, coinciding with the increase of H+–K+-ATPase mRNA expression and activity. Ghrelin acts on gastric mucosal cells to stimulate both mRNA expression and activity of H+–K+-ATPase in vitro.