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Prostaglandin E2 binding site distribution and subtype classification in the rabbit iris-ciliary body.
S Csukas1, P Bhattacherjee, L Rhodes
1Department of Ophthalmology and Visual Sciences, Kentucky Lions Eye Research Institute, University of Louisville, School of Medicine 40292.
Prostaglandins
|September 1, 1992
Summary
Specific binding sites for prostaglandin E2 (PGE2) were found predominantly in the rabbit ciliary body, primarily acting through the EP2 receptor subtype. This supports functional studies on the blood-aqueous barrier.
Area of Science:
- Ophthalmology
- Pharmacology
- Molecular Biology
Background:
- Prostaglandin E2 (PGE2) plays a role in ocular physiology, including the regulation of the blood-aqueous barrier.
- Understanding PGE2 receptor distribution is crucial for developing targeted ocular therapies.
Purpose of the Study:
- To characterize the distribution and subtype selectivity of prostaglandin E2 (PGE2) binding sites in rabbit ocular tissues.
- To correlate binding data with known functional effects of PGE2 on the blood-aqueous barrier.
Main Methods:
- Membrane preparations from rabbit iris-sphincter, iris, and ciliary body were used for binding assays.
- Tritium-labeled prostaglandin E2 (3H-PGE2) was employed to quantify specific binding sites.
- Scatchard analysis and competition assays with selective EP receptor agonists were performed.
Main Results:
- The majority of 3H-PGE2 binding sites were located in the ciliary body (46%), followed by the iris (37%) and iris-sphincter muscle (5%).
- Scatchard analysis in the ciliary body revealed a single binding site (Kd = 2.81 nM, Bmax = 84 fmoles/mg protein).
- Competition studies indicated that most ciliary body binding sites are of the EP2 subtype, with minimal EP1 and a small number of EP3 sites.
Conclusions:
- PGE2 binding sites are predominantly found in the ciliary body of rabbit eyes and are primarily of the EP2 receptor subtype.
- The EP2 selectivity of PGE2 binding sites in the ciliary body aligns with functional data showing EP2-mediated breakdown of the blood-aqueous barrier.