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 mu M produced an increase (Delta J(H+)) of 725 +/- 133 nmol.cm(-2).h(-1) from basal secretion, this effect being inhibited by mucosal omeprazole 100 mu M. Basal secretion was also sensitive to the combination of serosal forskolin (FK) 10 mu M + serosal isobutylmethylxanthine (IBMX) 100 mu M (Delta J(H+) = 793 +/- 239 nmol.cm(-2).h(-1)); this effect was insensitive to mucosa( 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 mu M, a potent calcium-sensing receptor (CaR) agonist, stimulated the basal secretion (Delta J(H+) = 340 +/- 81 nmol.cm(-2).h(-1)). The present results indicate that the add 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. (C) 2013 Elsevier Inc. All rights reserved.