Ontogenesis of gastric response to agonists and antagonists of acid secretion in fetal rat.

The responsiveness of fetal rat stomach to the main agonists and antagonists of acid secretion was examined in vivo on days 19 and 20 of gestation. Significant acidification of the gastric content was observed only in response to pentagastrin, gastrin G-17, histamine and carbamylcholine from day 20, when the fetal stomach starts secreting hydrochloric acid. Vagally-mediated stimulation of gastric acid secretion in response to 2-deoxyglucose was also demonstrated on day 20. The effects of cimetidine and atropine on stimulated acid secretion were observed to be specifically related to histamine and carbamylcholine respectively. The findings provide evidence that the fetal gastric mucosa is sensitive to the three primary stimuli of acid secretion at the point when differentiated parietal cells start secreting acid. They suggest that at the functional differentiation stage, distinct pathways exist in fetal rat stomach for the stimulation of hormonal and neural acid secretion.