Effects of fasting on the expression of gastrin, cholecystokinin, and somatostatin genes and of various housekeeping genes in the pancreas and upper digestive tract of rats.

It is generally accepted that while the gene expression of many gut hormones in the pancreas and upper digestive tract is influenced by the prandial state, the expression of house-keeping genes (used as internal standards) is stable. We have analysed how food deprivation affects the messenger (m) RNA expression of gastrin, cholecystokinin (CCK), and somatostatin and of house-keeping genes glyceraldehyde-3-phosphate dehydrogenase (GAPDH), beta-actin and 18S ribosomal (r) RNA. RNA, isolated from oxyntic, antral and duodenal mucosa and pancreas, was subjected to Northern blot analysis using complementary RNA probes. Compared to fed rats, food-deprived rats exhibited reduced mRNA expression of gastrin (antrum), somatostatin (antrum), CCK (duodenum), GAPDH (all tissues studied) and beta-actin (all tissues studied) and unchanged 18S rRNA expression. We conclude that the assessment of gut hormone mRNA expression may be greatly influenced by the choice of internal standard and that 18S rRNA is superior.