In vitro characterization of acid secretion in the gilthead sea bream (Sparus aurata) stomach

The gastric acid secretion of juvenile Sparus aurata was characterized in Ussing chambers; secretion rates were determined by a pH-stat method at pH 5.50 and bioelectrical parameters were measured in current-clamped tissues. The basal secretion equaled to 535 ± 87 nmol·cm− 2·h− 1. Serosal carbachol 100 μM produced an increase (ΔJH+) of 725 ± 133 nmol·cm− 2·h− 1 from basal secretion, this effect being inhibited by mucosal omeprazole 100 μM. Basal secretion was also sensitive to the combination of serosal forskolin (FK) 10 μM + serosal isobutylmethylxanthine (IBMX) 100 μM (ΔJH+ = 793 ± 239 nmol·cm− 2·h− 1); this effect was insensitive to mucosal omeprazole 100 mM but inhibited by mucosal bafilomycin A1 100 nM. The effect of carbachol proceeded within a few minutes (< 10 min), whereas the effect of FK + IBMX was gradual, taking 40 min to reach the maximum. The addition of mucosal gadolinium (Gd3 +) 100 μM, a potent calcium-sensing receptor (CaR) agonist, stimulated the basal secretion (ΔJH+ = 340 ± 81 nmol·cm− 2·h− 1). The present results indicate that the acid secretion mechanism in the sea bream stomach is regulated by muscarinic and CaR-like receptors, cAMP is implicated in the signal transduction, and at least two proton pumps, a HK-ATPase and a V-ATPase contribute to acid secretion.