Hypotensive effect of ZD7155, an angiotensin II receptor antagonist, parallels receptor occupancy in two-kidney, one-clip Goldblatt hypertensive rats

OBJECTIVE: To examine the effect of ZD7155, an angiotensin II receptor antagonist, on blood pressure, heart rate and occupancy of tissue angiotensin II receptor in two-kidney, one-clip Goldblatt hypertensive rats. METHODS: Goldblatt hypertension was produced in Sprague-Dawley rats. ZD7155 was administered orally at 3 mg/kg and blood pressure and heart rate were monitored for up to 48 h. In a second series of experiments, the rats were administered increasing doses of ZD7155 and monitored for 1 h. For each time and dose, rats were killed and their blood and tissues were collected. Tissue angiotensin II receptor binding was assessed by quantitative autoradiography in vitro. For a separate group of rats, the pressor response to 0.1 microg/kg angiotensin II was monitored before and after the administration of 3 mg/kg ZD7155. RESULTS: After oral administration of ZD7155, blood pressure was rapidly lowered and this lowering was sustained for up to 48 h. This effect was accompanied by sustained inhibition of angiotensin II receptor binding in the aorta, kidney and adrenal gland, together with an increase in plasma renin activity. Increasing doses of ZD7155 dose-dependently reduced blood pressure and inhibited angiotensin II receptor binding in the tissues. Degrees of inhibition varied among the different tissues and had different time courses. ZD7155 inhibited the pressor response to angiotensin II remarkably for 24 h. CONCLUSIONS: ZD7155 is a potent antihypertensive agent in two-kidney, one-clip Goldblatt hypertensive rats and this effect is accompanied by sustained inhibition of tissue angiotensin II binding.