Influence of growth hormone on cysteamine-induced gastro-duodenal lesions in rats: The involvement of somatostatin

It is known that cysteamine ulcerogenic effect depends, among others, on a depletion of somatostatin in the gastro-intestinal tract. Since growth hormone (GH) causes the release of hypothalamic somatostatin (SRIH) and potentiates the ulcerogenic action of cysteamine we have studied the influence of GH on gastro-duodenal mucosa levels of SRIH, and its relevance for the ulcerogenic action of cysteamine. Female rats of the Sprague-Dawley strain were pretreated with GH (0.25, 0.5 or 1 mg/kg) and subjected to cysteamine-induced gastric lesions. These animals showed an increased mortality and severity of gastric lesions. The measurement of gastric and duodenal barrier mucus levels revealed that GH administration was followed by a decrease in mucus production. Pretreatment with SRIH (25 or 50 mu g/kg) was followed by a decreased percent incidence and severity of gastric mucosa lesions induced by cysteamine. The mucus production was increased by SRIH administration. GH pretreatment was followed by a reduction of SRIH-like immunoreactivity in gastro-duodenal mucosa and an increase of insulin plasma levels. Acute injection of cysteamine per se was also followed by a decrease of gastro-duodenal SRIH and an increase in insulin plasma levels. These results suggest that high levels of plasma GH, as induced by exogenous GH administration, may cause a decrease of SRM gastro-intestinal content and this in turn may potentiate the ulcerogenic activity of cysteamine.