Angiotensin II-induced hypertension in the rat. Effects on the plasma concentration, renal excretion, and tissue release of prostaglandins.

We examined in rats the effects of intraperitoneal angiotensin II (AII) infusion for 12 d on urinary excretion, plasma concentration, and in vitro release of prostaglandin (PG) E2 and 6-keto-PGF1 alpha, a PGI2 metabolite. AII at 200 ng/min increased systolic blood pressure (SBP) progressively from 125 +/- 3 to 170 +/- 9 mmHg (P less than 0.01) and elevated fluid intake and urine volume. Urinary 6-keto-PGF1 alpha excretion increased from 38 +/- 6 to 55 +/- 5 and 51 +/- 7 ng/d (P less than 0.05) on days 8 and 11, respectively, of AII infusion, but urinary PGE2 excretion did not change. Relative to a control value of 129 +/- 12 pg/ml in vehicle-infused (V) rats, arterial plasma 6-keto-PGF1 alpha concentration increased by 133% (P less than 0.01) with AII infusion. Aortic rings from AII-infused rats released more 6-keto-PGF1 alpha (68 +/- 7 ng/mg) during 15-min incubation in Krebs solution than did rings from V rats (40 +/- 3 ng/mg); release of PGE2, which was less than 1% of that of 6-keto-PGF1 alpha, was also increased. Slices of inner renal medulla from AII-infused rats released more 6-keto-PGF1 alpha (14 +/- 1 ng/mg) during incubation than did slices from V rats (8 +/- 1 ng/mg, P less than 0.05), but PGE2 release was not altered. In contrast, AII infusion did not alter release of 6-keto-PGF1 alpha or PGE2 from inferior vena cava segments or from renal cortex slices. Infusion of AII at 125 ng/min also increased SBP, plasma 6-keto-PGF1 alpha concentration, and in vitro release of 6-keto-PGF1 alpha from rings of aorta and renal inner medulla slices; at 75 ng/min AII had no effect. SBP on AII infusion day 11 correlated positively with both 6-keto-PGF1 alpha plasma concentration (r = 0.54) and net aortic ring release (r = 0.70) when data from all rats were combined. We conclude that augmentation of PGI2 production is a feature of AII-induced hypertension. The enhancement of PGI2 production may be an expression of nonspecific alteration in vascular structure and metabolic functions during AII-induced hypertension, as well as the result of a specific effect of the peptide on the arachidonate-prostaglandin system.