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Bovine iris-sphincter muscle lacks FP receptor binding sites
P Bhattacherjee1, B S Williams, P Mukhopadhyay
1Department of Ophthalmology & Visual Sciences, University of Louisville, KY 40202, USA.
Ocular Immunology and Inflammation
|July 20, 1999
Summary
Tritium-labeled prostaglandin F2alpha binds to EP1 and EP3 receptors in bovine iris-sphincter muscle, not FP receptors. FP receptor mRNA is likely absent in the iris-sphincter muscle but present in the corpus luteum.
Area of Science:
- Pharmacology
- Molecular Biology
- Veterinary Medicine
Background:
- Prostaglandin F2alpha (PGF2α) plays a crucial role in various physiological processes.
- Understanding the specific prostaglandin receptors involved in different tissues is essential for targeted therapeutic interventions.
- The expression and function of prostaglandin receptors in bovine ocular and reproductive tissues require further elucidation.
Purpose of the Study:
- To determine the affinity, density, and specificity of binding sites for tritium-labeled prostaglandin F2alpha (³H-PGF2α) in bovine iris-sphincter muscle and corpus luteum membrane preparations.
- To investigate the presence and expression of FP receptors in these tissues using molecular methods.
Main Methods:
- Saturation and competition binding assays using ³H-PGF2α with varying concentrations of unlabeled PGF2α and other prostaglandin receptor agonists.
- Scatchard analysis to determine the dissociation constant (Kd) and maximum binding capacity (Bmax) in iris-sphincter muscle.
- Reverse transcription polymerase chain reaction (RT-PCR) to assess FP receptor mRNA expression in both tissues.
Main Results:
- Specific binding sites for ³H-PGF2α in bovine iris-sphincter muscle membranes showed saturable binding with an affinity (Kd) of 9.5 nM and a density (Bmax) of 596 fmoles/mg protein.
- Prostaglandin E2, 17-phenyl trinor prostaglandin E2, and GR63799 inhibited ³H-PGF2α binding in iris-sphincter muscle, suggesting interaction with EP1 and EP3 receptors.
- Fluprostenol, a specific FP receptor agonist, did not inhibit ³H-PGF2α binding in iris-sphincter muscle, but did in the corpus luteum, where PGF2α also effectively inhibited binding.
Conclusions:
- The bovine iris-sphincter muscle does not express FP receptors; instead, ³H-PGF2α binds to EP1 and EP3 receptor sites.
- RT-PCR analysis indicated the probable absence of FP receptor mRNA in the bovine iris-sphincter muscle, contrasting with its presence in the bovine corpus luteum.
- These findings suggest distinct prostaglandin receptor profiles in different bovine tissues, with implications for understanding PGF2α's actions.