Linkage between somatostatin and acid secretion: evidence from use of pertussis toxin

Pertussis toxin was used to examine the functional linkage between somatostatin and acid secretion and the mode of action of somatostatin at the cellular level in the isolated luminally perfused mouse stomach. Pretreatment of the stomach with pertussis toxin (125-1,250 ng/ml) for 60 min 1) caused a significant twofold increase in histamine-stimulated acid secretion (from 42 +/- 7 to 82 +/- 12 nmol/min; P less than 0.01) but not pentagastrin-stimulated secretion and 2) blocked the inhibitory effect of somatostatin on basal and histamine-stimulated acid secretion but not on pentagastrin-stimulated acid secretion. The ability of pertussis toxin to reverse selectively the inhibitory effect of somatostatin on histamine-stimulated acid secretion is consistent with the ability of pertussis toxin to inactivate a guanine nucleotide binding protein, which couples somatostatin receptors to inhibition of adenylate cyclase; histamine, but not gastrin, stimulates acid secretion via activation of adenylate cyclase. Secretagogue-stimulated acid secretion was accompanied by a parallel increase in somatostatin secretion that is largely determined by luminal acidity. The augmentation of histamine-stimulated acid secretion after treatment with pertussis toxin implied that the concomitant increase in somatostatin secretion is coupled to acid secretion and acts to attenuate it. The results confirm the role of gastric somatostatin as a paracrine regulator of acid secretion.