The role of ghrelin at the regulation of gastric acid secretion and mucus content

ABSTRACT The role of ghrelin at the regulation of gastric acid secretion and mucus content Bilgin M, Dicle University Medical Faculty,Department of Physiology. PhD Thesis, Diyarbakır, 2005. Purpose: Ghrelin has been proposed to stimulate gastric acid secretion.The postulated stimulatory effect of ghrelin on acid secretion has been proposed to be mediated by gastrin or by vagal stimulation. Nitric oxide is generally thought to play a role at the regulation of feeding. This activity of NO is inhibited by L-NAME(a NOS inhibitor). We tested this assumption by determining the gastric acid levels and mucus content in the rats that were taken ghrelin intravenously and the inhibitor of NO synthase activity (L-NAME) subcutaneously. So, the objective of the present study was to examine the possible effects of peripherally administered ghrelin and endogenous NO release on gastric acid secretion. Material and Methods: In this study, we used Wistar albino rats weighing 200-300 g. Before the experiments all rats were starved for 24 h, but had free access to tap water. We performed acid secretion studies by using the pylorus ligation method. The stimulated acid output after pylorus ligation reflects vagal excitation. Under light ether anesthesia, the pyloric sphincter was ligated through a small midline incision and the abdominal wall was closed. 20 ug/kg dose of ghrelin (dissolved in 1ml of saline) was injected intravenously at the time of pyloric ligation to the first group. In addition to i.v. ghrelin, 70 mg/kg L-NAME was performed subcutaneously to the second group. Saline infusion was performed to the control group. The animals were euthanized 3 h after pylorus ligation, the stomachs were removed and the gastric fluid were collected. The volume of supernatant was measured and diluted appropriately (1:20) for titration with 0.01 N NaOH to pH 7. Results: No statistical difference was determined between the control and the ghrelin group about gastric acid volume while there was a significant decrease at ghrelin+L- NAME group (p<0.01). The acid output was increased at ghrelin group (p<0.05) while it was decreased at ghrelin+L-NAME group (p<0.01). The increased plasma total nitrite levels at ghrelin group were significant against the other groups (p<0.01). There was no important statistical difference among the groups about plasma ghrelin VIlevels (p>0.05). The mucus content was higher at ghrelin group than the control group (p<0.05) while it was significantly lower at ghrelin+L-NAME group (p<0.01). Conclusion : In this study,we demonstrate that the gastric acid secretion was increased by administrating ghrelin while it was decreased by ghrelin+L-NAME infusion. Gastric mucus content was also increased by ghrelin infusion while it was decreased by ghrelin+L-NAME administration. Key Words: acid secretion, ghrelin, gastric mucus content VS