Enrichment and characterization of specific [3H]PGE2 binding sites in the porcine gastric mucosa.
[3H]Prostaglandin E2 (PGE2) binding sites were 10-fold enriched from a porcine fundic mucosal homogenate by differential centrifugation and subsequent discontinuous sucrose gradient separation. PGE2 bound with an activation energy of 66 kJ/mol to a single class of sites with an affinity of 1.5 +/- 0.4 nM and a capacity of 274 +/- 76 fmol/mg protein. There was no indication for any cooperativity between the binding sites. Kinetic analysis revealed a kon of 3 x 10(5) M x s-1 at 30 degrees C and pH 5.5. Dissociation was biphasic with an initial rapid (koff = 10(-3) s-1) and a subsequent slower phase (koff = 4 X 10(-5) s-1), presumably reflecting the existence of two interchangeable forms of [3H]PGE2 binding sites. The rank order of affinity for other prostanoids (PGE2 greater than PGE1 greater than PGA2 greater than iloprost (PGI2 derivative) greater than PGF2 alpha greater than PGB2 greater than PGD2) is discussed against the background of the recently postulated E-type receptors in the stomach.
D000818:Animals; D001667:Binding, Competitive / Q000187:drug effects; D015232:Dinoprostone; D011464:Epoprostenol / Q000494:pharmacology; D005753:Gastric Mucosa / Q000378:metabolism*; D016285:Iloprost; D066298:In Vitro Techniques; D007700:Kinetics; D011453:Prostaglandins / Q000494:pharmacology; D011458:Prostaglandins E / Q000378:metabolism*; D011982:Receptors, Prostaglandin / Q000378:metabolism*; D013552:Swine
D011453:Prostaglandins; D011458:Prostaglandins E; D011982:Receptors, Prostaglandin; D011464:Epoprostenol; D016285:Iloprost; D015232:Dinoprostone