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The evolution of malignant hypertension was studied under metabolic balance conditions in 11 uninephrectomized rats given deoxycorticosterone acetate and 1% NaCl as drinking water. Changes in sodium and potassium balance were related to changes in blood pressure, plasma renin activity, hematocrit, and kidney histology. After 3-4 weeks of steadily positive sodium balance accompanied by continuously increasing blood pressure up to 185 plus or minus 19 (SE) mm Hg, periods of sodium loss accompanied by evidence of hemoconcentration were observed marking the onset of the malignant phase as defined by the development of fibrinoid necrosis in the kidney. Plasma renin activity remained markedly suppressed both at the fourth week (0.33 plus or minus 0.02 ng/ml hour-1) when the sodium balance was positive and the kidney biopsy negative and at the end of the experiment (0.35 plus or minus 0.36 ng/ml hour-1) when the sodium balance was negative and the kidney histology revealed malignant vasculitis. Infusion of the angiotensin II inhibitor 1-Sar-8-Ala-angiotensin II consistently failed to affect blood pressure, and the kidney tissue norepinephrine level was reduced (0.054 plus or minus 0.01 mug/g) compared with the control level (0.132 plus or minus 0.02 mug/g). We conclude that malignant vasculitis in this model is preceded by hypertension associated with sodium and water retention and is accompanied by negative sodium balance, decreases in body weight, falling blood pressure, and hemoconcentration without demonstrable participation of the renin-angiotensin system or the renal catecholamines.
Gavras et al. (Sat,) studied this question.