Endogenous E-type prostaglandins in regulation of basal alkaline secretion by amphibian duodenum in vitro

Segments of proximal duodenum from Rana catesbeiana, stripped of external muscle and mounted as a tube in a glass chamber, alkalinized the luminal-side bathing solution at a rate of 1.70 +/- 0.16 microEq/cm . h (n = 18, gross surface area approximately 1.5 cm2/cm). A single change of the serosal-side bathing solution for fresh solution reduced the rate of titratable alkaline secretion, which achieved a new steady state after 45 min amounting to 66% +/- 2% of the initial rate; transmucosal potential difference (lumen negative) fell from 10.6 +/- 1.2 to 8.8 +/- 1.1 mV. Concentrations of E-type prostaglandins in the serosal-side solution measured by radioimmunoassay were 8.5 nM (3 ng/ml) before, 0.17 nM 5 min after, and 1.7 nM 90 min after the solution change (n = 8). Reapplication of the original bathing solution 90 min after the initial change reestablished original secretory rate and potential difference. The increases in alkaline secretion and potential difference were comparable in magnitude and profile to those induced by serosal administration of 10 nM prostaglandin E2. Addition of the metabolic inhibitor 2,4-dinitrophenol (100 microM, serosal side) reduced basal alkaline secretion to 30% +/- 7% of the initial rate and abolished the potential difference (n = 8). These data demonstrate that endogenous prostaglandin E production by an isolated preparation of amphibian duodenum accounts for a proportion of alkaline secretion that is equivalent to 50% of metabolism-dependent basal secretion.