Bicarbonate secretion in isolated guinea pig antrum.

HCO3- secretion was investigated in isolated guinea pig antral mucosa mounted in Ussing chambers. The rate of HCO3- secretion was measured by a pH-stat system. The antral mucosa spontaneously secreted HCO3- at a rate of about 0.5 microEq cm-2 h-1. Bethanechol (100 microM) or 8-bromoadenosine 3':5'-cyclic monophosphate (8-Br-cAMP, 1 mM) induced a significant increase in HCO3- secretion. Prostaglandin E2 (1 microM) also produced an increase in HCO3- secretion, although it was less effective than either bethanechol or 8-Br-cAMP. Histamine (100 microM) did not affect HCO3- secretion. This preparation may be suited to the study of the precise mechanisms by which neurohumoral factors regulate gastric HCO3- secretion.