Prostaglandin D2 diminishes transmucosal potential difference in rat colonic mucosa in vitro in contrast to the increasing effect of prostaglandin E1

Effect of prostaglandin F2 alpha on transmural potential difference and short-circuit current in isolated frog (Rana catesbeiana) skin

1. Addition of prostaglandin F2 alpha to the inside bathing solution elicited sustained decreases in transmural potential difference and short-circuit current. 2. Addition of indomethacin to the inside bathing solution partially inhibited transmural potential difference and short-circuit current. 3. Addition of indomethacin to the inside bathing solution further decreased the prostaglandin F2 alpha effect on transmural potential difference and short-circuit current. 4. The prostaglandin F2 alpha-induced effects on short-circuit current were carried by a net active sodium transfer from the outside to the inside bathing solution.

Inhibition of neuronally mediated secretion in rat colonic mucosa by prostaglandin D2

The effect of prostaglandin D2 (PGD2) on ion transport across the mucosa of the descending colon was studied in rats. PGD2 dose-dependently decreased baseline short-circuit current of mucosa-submucosal preparations mounted either in the Ussing chamber or mounted as an everted sac. However, with the everted sac technique, the tissue was about 1000 times more sensitive to PGD2. Concomitant with the decrease in short-circuit current, PGD2 increased the mucosal-to-serosal fluxes of sodium and chloride and decreased the serosal-to-mucosal flux of chloride. PGD2 inhibited the secretory action of the PGI2 analogue iloprost, PGD2 alpha, and neurotensin. The action of these secretagogues was dependent on the presence of the submucosal plexus. In contrast, PGD2 had no effect on the increase in short-circuit current caused by PGD2, substance P, or serotonin, the actions of which were not dependent on the presence of the submucosal plexus. The results indicate that the action site of the antisecretory mechanism of PGD2 is localized in the secretomotor neurons.

Characterization of the antisecretory action of prostaglandin D2 in the rat colon

Previous studies have shown that prostaglandin D2 (PGD2) inhibits neuronally mediated secretion in the rat colon. This antisecretory action of PGD2 was further characterized by the use of a prostaglandin D receptor blocker. Prostaglandin D2 inhibited the neuronally mediated short-circuit current evoked by prostaglandin I2, which represents Cl- secretion. The concentration-response curve for the inhibition by PGD2 was shifted to the right in the presence of the prostaglandin D receptor blocker, AH 6809. AH 6809 had no effect on the short-circuit current response induced by prostaglandin E2 or iloprost, a stable prostaglandin I2 analogue, suggesting an interaction of the blocker with receptors specific for PGD2. A direct interaction of PGD2 with enteric neurones was studied by determining its effect on acetylcholine release from enteric neurones preloaded with [3H]choline. Prostaglandin D2 suppressed 3H release induced by electric field stimulation. It had, however, no effect on the release induced by depolarization with potassium. The results suggest that the inhibitory action of PGD2 on enteric cholinergic neurones is mediated by prostaglandin D receptors.