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Prostaglandin E2 binding sites in bovine iris-ciliary body
P Bhattacherjee1, S Csukas, C A Paterson
1Department of Ophthalmology and Visual Sciences, Kentucky Lions Eye Research Institute, University of Louisville 40202.
Investigative Ophthalmology & Visual Science
|June 1, 1990
Summary
Researchers found specific binding sites for prostaglandin E2 (PGE2) in bovine eye tissue. This selectivity suggests PGE2 plays a key role in ocular physiology and potential therapeutic targets.
Area of Science:
- Ocular Physiology
- Biochemistry
- Pharmacology
Background:
- Prostaglandins (PGs), like PGE2 and PGF2 alpha, influence ocular functions including vasodilation and intraocular pressure.
- Understanding PG receptor interactions is crucial for elucidating their physiological roles in the eye.
Purpose of the Study:
- To investigate the specificity and selectivity of prostaglandin E2 (PGE2) receptors.
- To characterize PGE2 binding sites within bovine iris-ciliary body (ICB) membrane preparations.
Main Methods:
- Preparation of pigment-free bovine ICB membranes using sucrose density-gradient centrifugation.
- Incubation of membranes with radiolabeled 3H-PGE2 and varying concentrations of unlabeled PGE2 or F2 alpha.
- Analysis of binding kinetics, including IC50, Kd, and Bmax values, using competition assays and Scatchard analysis.
Main Results:
- Specific binding of 3H-PGE2 to ICB membranes was observed, with 80% of total binding being specific.
- Unlabeled PGE2 demonstrated a significantly higher affinity (IC50 = 3 nM) than F2 alpha (IC50 = 379 nM), indicating ~100-fold selectivity for PGE2.
- Scatchard analysis suggested a single class of binding sites with a dissociation constant (Kd) of 13.3 nM and a maximum binding capacity (Bmax) of 156 fmoles/mg protein.
Conclusions:
- The bovine ICB possesses binding sites with high selectivity for PGE2 over F2 alpha.
- These findings support the existence of specific PGE2 receptors in the bovine iris-ciliary body.
- This selectivity is important for understanding the physiological effects of PGE2 in the eye.