PGE2 receptors and their intracellular mechanisms in rabbit small intestine

The effects of PGE2 on longitudinal smooth muscle, the intracellular mechanisms involved, and the localization of EP receptors were investigated in rabbit small intestine. PGE2 evoked contractions in small intestine that were reduced by tetrodotoxin and hexamethonium. 17-Phenyl trinor PGE2, sulprostone, misoprostol and 16,16-dimethyl PGE2 evoked contractions. Butaprost did not modify spontaneous motility. AH 6809 reduced PGE2 and 17-phenyl trinor PGE2-induced contractions. Verapamil, Ca2+ free medium, staurosporine, forskolin, theophylline, and rolipram diminished, while IP-20 and H-89 increased PGE2-induced contractions. Western blot analysis showed protein bands of 41 kDa for EP1, 71 kDa for EP2 and 62 kDa for EP3 receptors. EP1, EP2 and EP3 receptors were detected in neurons of the myenteric and submucosal ganglia, but only EP3 receptors were found in smooth muscle layers. This study did not detect EP4 receptor. PGE2-induced contractions would be mediated through EP1 and EP3 receptors, and voltage-dependent Ca2+ channels, protein kinase C, and cAMP would be implicated in these responses.