CHARACTERIZATION OF PGE(2) RECEPTORS IN ISOLATED RABBIT COLONIC CRYPT CELLS

The physiological effects of prostaglandins (PG) are mediated through their interactions with specific receptors on effector cells. In this study the properties of PGE(2) receptors in the rabbit distal colon were examined. We report the presence of specific, saturable, and high-affinity binding sites of PGE(2) of the EP(2) subtype in isolated colonic crypts. Scatchard analysis revealed the presence of two binding sites with dissociation constants of 0.3 and 10.8 nM and corresponding maximum number of receptors of 15 and 134 fmol/10(6) cells. From competition experiments in the presence of guanosine 5'-O-(3-thiotriphosphate), PGE(2) binding was decreased, suggesting that the receptor is coupled to a G protein. No PGE(2) binding sites were detected in surface cells. Levels of adenosine 3',5'-cyclic monophosphate (cAMP) were measured in isolated epithelial cells after being exposed to different concentrations of PGE(2). cAMP levels were significantly increased only in the crypt cells when exposed to PGE(2). These data provide the first demonstration for the existence of PGE(2) receptors on colonic crypt cells, which when activated lead to increased levels of cAMP.