The failure of furosemide-induced salt and water loss to convert benign to malignant hypertension in the rat.

The concept has been advanced that malignant hypertension is precipitated in the rat with renal hypertension by a sudden loss of sodium in the urine. In order to test this hypothesis modest degrees of hypertension were produced in Holtzman rats by the application of a silver clip to one renal artery, not touching the opposite kidney. When the systolic blood pressure reached a level between 160 and 180 mm Hg, loss of sodium and water was induced by the administration of furosemide, given either orally over a 7-day period, or by 3 intramuscular injections over a 24-hour period. Sodium and water balance studies, blood pressure determinations, histologic assessment of blood vessels in the nonclipped kidney, and measurement of activity of the juxtaglomerular apparatus were carried out in these 2 groups and appropriate control animals. It was found that in spite of a considerable natriuresis and diuresis in furosemide-treated animals, there was neither a significant increase in the blood pressure nor development of more severe vascular lesions in the nonclipped kidney than in the kidneys of control animals.