Regulation of gastric somatostatin gene expression.

Regulation of somatostatin gene expression was studied in the rat gastric antrum. Antral total RNA was isolated from animals during starvation and after refeeding, or under gastric neutralization by fundectomy or by omeprazole treatment. Northern blot analysis using cRNA probe synthesized from a cloned rat somatostatin cDNA demonstrated a single hybridizing band, approximately 850 nucleotides in length, which is present in the antrum. Quantitative slot blot analyses were able to detect significant changes of somatostatin mRNA levels in total RNA as low as 5 micrograms. Somatostatin mRNA levels increased significantly after 12 hours of fasting (144% of control) and remained elevated throughout the 4-day fasting period. Upon refeeding with solid food and phenylalanine, antral somatostatin returned to the prefasted level in 2 hours. Refeeding with olive oil or saline depressed somatostatin mRNA significantly within 30 to 60 minutes but did not attain the prefasted state. Fundectomy and omeprazole resulted in maximal inhibition of antral somatostatin mRNA levels by 77% and 78%, respectively. The present in vivo results indicate that somatostatin gene expression in the stomach is regulated by luminal factors that include pH and specific nutrients. Future studies based on this phenomenon can expand knowledge of the interactions between gastric endocrine cells and the gastric environment.