Renal hemodynamics in acute and chronic angiotensin II hypertension

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Abstract
Sequential changes in arterial pressure (AP), renal hemodynamics, body fluid and electrolyte balance and plasma aldosterone concentration (PAC) were examined during acute and chronic i.v. infusions of angiotensin II (AII) (10 ng/kg per min) in 8 conscious dogs maintained on 103 meq/day Na intake. Within 20 min after the start of AII infusion, AP increased 24 .+-. 2 mmHg; during the next 4 days AP increased further, stabilizing at 38 .+-. 4 mmHg above control. Coinciding with the rise in AP on days 1 and 2 was a marked retention of H2O and Na and a rise in Na iothalamate space to 108 .+-. 1 and 111 .+-. 2%, respectively, of control value. Effective renal plasma flow (ERPF) decreased to 85 .+-. 5% of control and remained at this level throughout the study, but glomerular filtration rate decreased only 5-8% during acute infusions and was not significantly altered during chronic AII infusion. Although PAC increased markedly during the first 100 min of AII infusion, after 1 day PAC declined to values only slightly greater than control. During chronic AII hypertension, the direct renal hemodynamic (decreased ERPF and increased filtration fraction) or tubular effects of AII, rather than changes in PAC, may be primarily responsible for the tendency toward Na and H2O retention that occurs until AP increases enough to achieve Na and H2O balance.