[Changes in responses of blood pressure and several hormones to infusions of angiotensin II and angiotensin III in patients with essential hypertension].

In this study, the effects of angiotensin II (A II, Asn-Arg-Val-Tyr-Val-His-Pro-Phe) and angiotensin III (A III, Arg-Val-Tyr-Ile-His-Pro-Phe) on blood pressure (B.P.), pulse rate, several hormones [plasma renin activity (PRA), plasma aldosterone (PA), ACTH, plasma cortisol (PC), urinary catecholamines and urinary aldosterone] and urinary electrolytes were investigated in 9 male patients with essential hypertension [mean age 36.2 +/- 4.1 (S.E.) years]. A II and A III infusions (8 ng/kg/min, 60 min) were started from 0900 h and blood samples were drawn before, at 15, 30, 45, 60 min after the beginning of the infusions, and at 15 min after their cessation. Urinary samples were collected within 2 hrs before and after the infusions, respectively. A II significantly increased B.P.(p less than 0.01) during the infusions, whereas A III did not increase B.P.. PRA significantly decreased after the infusions of A II and A III (p less than 0.05), but the potency of A II was significantly greater than that of A III (p less than 0.01). PA was increased after both infusions, but in response to A III, a peak was observed at 30 min after the infusion and subsequently, the levels decreased gradually. Significant differences between both responses were found at 45 and 60 min (p less than 0.05) after the infusions. ACTH was unchanged during the infusions, but PC was equipotentially suppressed during the infusions, with the suppression of A II being similar to that of A III. In the responses of urinary catecholamines, noradrenaline and dopamine were equipotentially decreased after the infusions (p less than 0.05). The results of the present study clearly indicate that several differences exist between the biological activities of A II and those of A III. Further systematic experimental studies are needed to resolve the details.