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Pharmacological differences between rat and human endothelin B receptors
E E Reynolds1, O Hwang, M A Flynn
1Department of Cardiovascular Therapeutics, Parke-Davis Pharmaceutical Research, Division of Warner-Lambert Company, Ann Arbor, Michigan 48105, USA.
Biochemical and Biophysical Research Communications
|April 17, 1995
Summary
Despite high similarity, rat and human endothelin-B receptors (ETBR) exhibit distinct pharmacological profiles. Differences in binding affinities were observed for specific agonists and antagonists, highlighting interspecies variations in ETBR function.
Area of Science:
- Pharmacology
- Molecular Biology
- Biochemistry
Background:
- Endothelin-B receptors (ETBR) play crucial roles in physiological processes.
- Understanding species-specific receptor differences is vital for drug development.
- Rat and human ETBR share high sequence homology.
Purpose of the Study:
- To investigate potential pharmacological distinctions between cloned rat and human endothelin-B receptors (ETBR).
- To compare the binding affinities of various agonists and antagonists to rat and human ETBR.
Main Methods:
- Recombinant rat and human ETBR were expressed in Chinese Hamster Ovary-K1 (CHO-K1) cells.
- Radioligand binding assays using [125I]-ET-3 were performed.
- Affinity constants (Ki) for various ETBR ligands were determined for both species.
Main Results:
- Both rat and human ETBR showed similar affinities for several known ETBR agonists and antagonists.
- Significant differences in binding affinities were observed for specific peptide and non-peptide antagonists, with Ki value variations ranging from 4.1- to 53.4-fold.
- The ETBR-selective agonist IRL 1620 exhibited a 5.7-fold higher affinity for rat ETBR compared to human ETBR.
Conclusions:
- Rat and human ETBR, despite high homology, display significant pharmacological differences.
- These interspecies variations in ligand binding affinities have implications for the interpretation of preclinical data and the development of targeted therapies.