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Nonpeptide angiotensin II receptor antagonists. III. Structure-function studies.
A T Chiu1, J V Duncia, D E McCall
1Medical Products Department, E.I. du Pont de Nemours & Company, Wilmington, Delaware.
The Journal of Pharmacology and Experimental Therapeutics
|September 1, 1989
Summary
New imidazole derivatives show significantly higher affinity for the angiotensin II (AII) receptor than the original compound S-8308. These novel compounds, EXP6155, EXP6159, and EXP6803, demonstrate potent competitive antagonism of AII receptors in various assays.
Area of Science:
- Medicinal Chemistry
- Pharmacology
- Cardiovascular Research
Background:
- The angiotensin II (AII) receptor is a key target for managing cardiovascular diseases.
- Improving the affinity of existing AII receptor antagonists is crucial for developing more effective therapies.
Purpose of the Study:
- To synthesize and evaluate novel 1-benzylimidazole-5-acetate derivatives with enhanced affinity for the AII receptor.
- To characterize the mechanism of action and potency of these new compounds.
Main Methods:
- Synthesis of imidazole-5-acetate derivatives with varying phenyl ring substituents.
- Inhibition of [3H]AII binding to rat adrenal cortical microsomes.
- Scatchard analysis to determine binding kinetics.
- In vitro and in vivo assays including smooth muscle cell binding, 45Ca++ influx, aortic ring contraction, and pressor response in rats.
Main Results:
- EXP6155, EXP6159, and EXP6803 exhibited 9-, 35-, and 107-fold higher affinity, respectively, than S-8308 for the AII receptor.
- Scatchard analysis indicated competitive antagonism by EXP6155.
- Potency order was saralasin > EXP6803 > EXP6159 > EXP6155 > S-8308 across multiple assays.
- No significant effects on norepinephrine or KCl responses, or on angiotensin-converting enzyme and renin activity.
Conclusions:
- The synthesized imidazole-5-acetate derivatives represent potent AII receptor antagonists.
- These compounds demonstrate competitive antagonism and improved affinity, offering potential for novel antihypertensive agents.
- Further investigation into their therapeutic potential is warranted.