Effects of Rioprostil on Bicarbonate Secretion by Guinea-pig Gastric Mucosa in vitro

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Abstract
Spontaneous and prostaglandin-stimulated HCO3 secretions are studied in guinea-pig isolated gastric mucosa by means of pH-stat techniques. Antral mucosa exhibits a spontaneous HCO3- secretion of about 0.5 mumol/cm2h that is almost abolished by serosal addition of indomethacin (10(-5) mol/l). Fundic HCO3- secretion of the same magnitude is revealed upon suppression of acid secretion by serosal omeprazole (10(-5) mol/l). It is stimulated by serosal or mucosal addition of either PGE1, the synthetic primary alcohol analogue of PGE1, rioprostil, or dimethyl-PGE2. Effective concentrations range from 10(-4) to 10(-6) mol/l. Short-circuit current remains unchanged, arguing against involvement of electrogenic mechanisms of HCO3- secretion. Tissue conductance increases in the presence of all compounds tested, but only during luminal exposure to rioprostil does this increase go beyond that observed in time controls. Thus, enhanced HCO3- secretion seems to be due to cellular mechanisms rather than to a rise in passive (paracellular) HCO3- flow.