Prostaglandin E2 modulates serotonin- and gastrin/CCK-immunoreactive cells in the duodenal mucosa of the rat.

Groups of Sprague-Dawley rats were given placebo or prostaglandin E2 (PGE2) at 25 or 5,000 micrograms/kg or 15,R,15-methyl-PGE2 (MePGE2) at 5 or 50 micrograms/kg, twice daily, orally, for 1 month. Histological sections from the proximal duodenum were processed for immunohistochemistry and the volume density of immunoreactive endocrine cells was determined using point-counting grids. The surface density of the villous lining was estimated by using a cycloid test system. Thereafter, the total volumes of endocrine cells and the total surface area of the villous lining were calculated after estimating the mucosal volume. The volume density of serotonin-immunoreactive cells was increased in the duodenum of rats given 25 or 5,000 micrograms/kg PGE2 (p < 0.05). The total volume of these cells increased in the animals given 25 micrograms/kg PGE2 (p < 0.05). The total volume of gastrin/CCK-immunoreactive cells was higher in rats given 25 micrograms/kg PGE2 or 50 micrograms/kg MePGE2 than in controls (p < 0.05). The volume density of somatostatin-immunoreactive cells increased in rats given 5 micrograms/kg MePGE2, but the total volumes were not different between the groups. The area of somatostatin-immunoreactive cell profiles was enlarged in the animals given 5,000 micrograms/kg PGE2 (p < 0.05). The mucosal volume was enlarged by prostaglandins. The epithelial thickness increased in rats given the highest doses of PGE2 (p < 0.05). The concentration of motilin-like immunoreactivity increased in the duodenum of rats given 5 micrograms/kg MePGE2 (p < 0.05). We conclude that oral administration of PGE2 for 1 month increased the total volumes of serotonin- and gastrin-CCK-immunoreactive cells and the tissue concentration of motilin-like immunoreactivity, which indicates that prostaglandins modulate endocrine cells in a stable steady-state condition.