Topographical studies on histamine- and adrenaline-sensitive adenylate cyclases in gastric and duodenal mucosa of human beings.

The distribution of histamine- and catecholamine-sensitive adenylate cyclases in human gastric and duodenal mucosa was studied. Basal enzyme activities averaged 155 pmol cAMP/mg prot./15 min in fundic gastric mucosa, 305 pmol cAMP/mg prot./15 min in the antral and 344 pmol cAMP/mg prot./15 min duodenal mucosa. 1 mM histamine induced a more than 2-fold increase of enzyme activity in fundic homogenates, whereas this secretagogue was nearly ineffective in similar preparations from the antral region (1.2-fold increase of enzyme activity). The response towards adrenaline was virtually identical in fundic and antral mucosa preparations. The duodenal enzyme was insensitive toward this catecholamine as well as to histamine. The data are suggestive for a messenger function of cAMP in histamine-stimulated gastric acid secretion.