The gastric acid secretion of juvenile Sparus aurata was characterized in Ussing chambers; secretion rates were determined by a pH-stat method at pH5.50 and bioelectrical parameters were measured in current-clamped tissues. The basal secretion equaled to 535±87nmol·cm(-2)·h(-1). Serosal carbachol 100μM produced an increase (ΔJH(+)) of 725±133nmol·cm(-2)·h(-1) from basal secretion, this effect being inhibited by mucosal omeprazole 100μM. Basal secretion was also sensitive to the combination of serosal forskolin (FK) 10μM+serosal isobutylmethylxanthine (IBMX) 100μM (ΔJH(+)=793±239nmol·cm(-2)·h(-1)); this effect was insensitive to mucosal omeprazole 100mM but inhibited by mucosal bafilomycin A1 100nM. The effect of carbachol proceeded within a few minutes (<10min), whereas the effect of FK+IBMX was gradual, taking 40min to reach the maximum. The addition of mucosal gadolinium (Gd(3+)) 100μM, a potent calcium-sensing receptor (CaR) agonist, stimulated the basal secretion (ΔJH(+)=340±81nmol·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.

http://www.ncbi.nlm.nih.gov/pubmed/24126049?dopt=Abstract