Prostaglandin E2 binding sites in bovine iris-ciliary body.
In the eye, prostaglandins (PGs), in particular PGE2 and PGF2 alpha, may induce vasodilation, disruption of the blood-aqueous barrier, and biphasic effects on intraocular pressure, depending on the species. The initial event leading to many of these physiologic responses is the interaction between the PG and a receptor. We have explored the specificity and selectivity of PGE2 receptors in bovine iris-ciliary body (ICB) membrane preparations. Pigment-free bovine ICB membranes were prepared by high-speed sucrose density-gradient centrifugation. Membranes were incubated with 1 nM 3H-PGE2 in the presence or absence of varying concentrations of unlabeled PGE2 or F2 alpha. Binding of 3H-PGE2 to membranes at 37 degrees C increased linearly with protein concentration, and binding reached equilibrium in 30 min. Specific PGE2 binding represented 80% of total 3H-PGE2 binding. Studies with unlabeled PGE2 or F2 alpha, as competing ligands, showed a dose-dependent inhibition of 3H-PGE2 specific binding. The IC50 for unlabeled PGE2 and F2 alpha was 3 and 379 nM, respectively, which suggests a 100-fold greater selectivity of the binding sites for PGE2 over F2 alpha. Scatchard analysis of saturation data revealed a mean Kd value of 13.3 nM with a Bmax of 156 fmoles bound/mg protein. The general linearity of our Scatchard plots tends to suggests a single class of binding sites for PGE2, although more than a single binding site could be present. These results indicate that binding sites selective for PGE2 exist in the bovine ICB.
Bhattacherjee
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P
Department of Ophthalmology and Visual Sciences, Kentucky Lions Eye Research Institute, University of Louisville 40202.
Csukas
S
S
Paterson
C A
CA
D000818:Animals; D001667:Binding, Competitive; D002417:Cattle; D002462:Cell Membrane; D002924:Ciliary Body / Q000032:analysis*; D015237:Dinoprost / Q000378:metabolism; D015232:Dinoprostone / Q000378:metabolism*; D007498:Iris / Q000032:analysis*; D007679:Kidney Medulla / Q000032:analysis; D007700:Kinetics; D011869:Radioligand Assay; D051381:Rats; D011982:Receptors, Prostaglandin / Q000032:analysis*; D018078:Receptors, Prostaglandin E
D011982:Receptors, Prostaglandin; D018078:Receptors, Prostaglandin E; D015237:Dinoprost; D015232:Dinoprostone