Effect of 15(R),15-methyl prostaglandin E2 and indomethacin on pancreatic secretion in man

Putative interaction of brush cells with bicarbonate secreting cells in the proximal corpus mucosa

The gastric epithelium is protected from the highly acidic luminal content by alkaline mucus which is secreted from specialized epithelial cells. In the stomach of mice strong secretion of alkaline fluid was observed at the “gastric groove,” the border between corpus and fundus mucosa. Since this region is characterized by numerous brush cells it was proposed that these cells might secrete alkaline solution as suggested for brush cells in the bile duct. In fact, it was found that in this region multiple cells express elements which are relevant for the secretion of bicarbonate, including carbonic anhydrase (CAII), the cystic fibrosis transmembrane conductance regulator (CFTR) and the Na⁺/H⁺ exchanger (NHE1). However, this cell population was distinct from brush cells which express the TRP-channel TRPM5 and are considered as putative sensory cells. The location of both cell populations in close proximity implies the possibility for a paracrine interaction. This view was substantiated by the finding that brush cells express prostaglandin synthase-1 (COX-1) and the neighboring cells a specific receptor type for prostaglandins. The notion that brush cells may be able to sense a local acidification was supported by the observation that they express the channel PKD1L3 which contributes to the acid responsiveness of gustatory sensory cells. The results support the concept that brush cells may sense the luminal content and influence via prostaglandins the secretion of alkaline solution.

Duodenal mucosal bicarbonate secretion in pigs is accompanied by compensatory changes in pancreatic and biliary HCO3- secretion

BACKGROUND

The purpose of the study was to examine the effect of stimulation and inhibition of duodenal mucosal bicarbonate secretion on pancreatic and hepatic bicarbonate secretion in response to acid.

METHODS

The effect of inhibition (indomethacin) or stimulation (misoprostol) of duodenal mucosal bicarbonate secretion on pancreatic and biliary bicarbonate secretion in response to intraduodenal infusion of HCl or intravenous infusion of secretin was studied in anaesthetized pigs.

RESULTS

The hepatic and pancreatic response to exogenous secretin was not significantly altered by stimulation/inhibition of duodenal bicarbonate secretion. However, pancreatic and biliary bicarbonate secretion in response to duodenal acidification was significantly augmented by inhibition of duodenal mucosal bicarbonate secretion; conversely, it was reduced by stimulation of duodenal bicarbonate secretion. The increase in plasma secretin levels in response to duodenal acidification was reduced by stimulation and augmented by inhibition of duodenal mucosal bicarbonate secretion.

CONCLUSIONS

Duodenal mucosal bicarbonate secretion can serve as a modulator of both pancreatic and biliary bicarbonate secretion in response to luminal acidification, possibly through regulation of the release of secretin.

The effect of dimethyl PGE2 on canine pancreatic autograft exocrine secretion

This study was designed to evaluate the effect of 16,16-dimethyl prostaglandin E2 (dimethyl PGE2) on exocrine secretion in autografted animals with pancreaticocystostomies. The rates of secretion of urinary (autograft) amylase (units/min) and bicarbonate (mmole/min), over a 5-hr interval, were determined in the basal state (Group A, N = 5), after a bolus injection of 1 microgram/kg of dimethyl PGE2 (Group B, N = 5), during an OP-CCK infusion at 125 ng/kg/hr (Group C, N = 5), and during an OP-CCK infusion plus a bolus injection of 1 microgram/kg (Group D, N = 5) or 18 micrograms/kg (Group E, N = 5) of dimethyl PGE2 at the end of the second hour. Basal secretion of amylase and bicarbonate were decreased 1 hr after 1 microgram/kg of dimethyl PGE2, with the bicarbonate inhibition being statistically significant (Group A = 0.073 +/- 0.04 vs Group B = 0.001 +/- 0.00; P less than 0.05). When compared to Group C (128.3 +/- 28.0), an immediate and significant inhibition of OP-CCK-stimulated amylase release was demonstrated in both Group D (36.3 +/- 11.1; P less than 0.02) and Group E (57.3 +/- 13.4; P less than 0.05). One and two hours post-dimethyl PGE2, amylase releases were 37.7 +/- 8.6 and 64.7 +/- 6.8 in Group D and 0.92 +/- 0.3 and 8.28 +/- 2.6 in Group E, compared to 140.3 +/- 23.3 and 104.9 +/- 31.8 in Group C, indicating a dose-related, prolonged inhibition of autograft amylase secretion.(ABSTRACT TRUNCATED AT 250 WORDS)