In vitro inhibition of gastric acid secretion by vasopressin

Interpretation of studies designed to investigate the inhibitory action of vasopressin on gastric acid secretion has proven difficult, as the in vivo models are potentially susceptible to both direct (e.g. mucosal effects) and indirect effects (e.g. changes in mucosal blood flow). In the present series of experiments we studied vasopressin inhibition of both basal and histamine-stimulated acid secretion in rat isolated gastric mucosa, a preparation which is independent of blood flow. Basal and histamine-stimulated levels of acid secretion were 2.32 +/- 0.10 (mean +/- S.E.) and 4.36 +/- 0.41 mu eqH+/h per cm2. Vasopressin inhibited both basal and histamine-stimulated acid secretion; the effect, which was maximal at 15 min post-dosing, was blocked by the specific V1 antagonist d(CH2)5Tyr(Me) AVP. No effect on acid secretion was evident with either the potent V2 agonist, dDAVP, or oxytocin, a neurohypophyseal hormone which can also affect water retention and blood pressure. These studies demonstrate that vasopressin can specifically inhibit mucosal acid secretion; the inhibitory effect is most likely mediated via a V1 vasopressin receptor subtype on the gastric mucosa.