Nonpeptide angiotensin II receptor antagonists. VIII. Characterization of functional antagonism displayed by DuP 753, an orally active antihypertensive agent.

In the spinal pithed rat, DuP 753, 2-n-butyl-4-chloro-5-hydroxy-methyl-1-[(2'-(1H-tetrazol-5-yl)biphe nyl-4-yl) methyl] imidazole potassium salt, inhibited competitively the pressor response to angiotensin II (AII), whereas saralasin showed a noncompetitive pattern of interaction. It did not alter the pressor responses to vasopressin and norepinephrine as well as the heart rate response to isoproterenol. In the anesthetized rat, DuP 753 did not affect the vasodepressor response to bradykinin. Given p.o. or i.v., DuP 753 did not lower blood pressure in conscious normotensive rats, but it inhibited the pressor response to AII but not to vasopressin. It lowered blood pressure in furosemide-treated normotensive rats. Unlike saralasin, DuP 753 did not cause a transient increase in blood pressure even at 100 mg/kg i.v. DuP 753 at 3.5 micrograms i.c.v. inhibited the pressor response to i.c.v. AII, whereas DuP 753 at 10 mg/kg p.o. did not, suggesting that a single p.o. administration of DuP 753 does not affect brain AII receptors which are accessible by i.c.v. injection. Our study indicates that DuP 753 is a p.o. active, nonpeptide, selective, competitive AII receptor antagonist.