CHARACTERIZATION OF PGE(2) RECEPTORS IN ISOLATED RABBIT COLONIC CRYPTCELLS

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 we re examined. We report the presence of specific, saturable, and high-a ffinity binding sites of PGE(2) of the EP(2) subtype in isolated colon ic crypts. Scatchard analysis revealed the presence of two binding sit es with dissociation constants of 0.3 and 10.8 nM and corresponding ma ximum number of receptors of 15 and 134 fmol/10(6) cells. From competi tion experiments in the presence of guanosine 5'-O-(3-thiotriphosphate ), PGE(2) binding was decreased, suggesting that the receptor is coupl ed to a G protein. No PGE(2) binding sites were detected in surface ce lls. Levels of adenosine 3',5'-cyclic monophosphate (cAMP) were measur ed in isolated epithelial cells after being exposed to different conce ntrations of PGE(2). cAMP levels were significantly increased only in the crypt cells when exposed to PGE(2). These data provide the first d emonstration for the existence of PGE(2) receptors on colonic crypt ce lls, which when activated lead to increased levels of cAMP.