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S G Duffy
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What stimulates the renin-angiotensin system in rats with two-kidney renal hypertension?
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Exchangeable sodium, plasma renin activity and blood pressure changes during the development of 2 kidney 1 clip hypertension, and after subsequent contralateral nephrectomy.
Sequential changes in exchangeable sodium, fluid intake, blood pressure and plasma renin activity were measured in 2K1C hypertensive rats during the development of severe hypertension. Exchangeable sodium was measured by the equilibration of the rats' exchangeable sodium with radioactive saline. In rats drinking saline, both PRA and exchangeable sodium levels increased as hypertension developed, and captopril induced large falls in blood pressure. Subsequent removal of the contralateral kidney reduced PRA, but did not alter exchangeable sodium or blood pressure. Captoril had no effect on blood pressure. It is concluded that the rise in PRA in 2K1C hypertension depends on the presence of the contralateral kidney, but occurs in the absence of sodium depletion.
Sodium balance and plasma renin activity during the development of two-kidney Goldblatt hypertension in rats.
1. In two experiments severe hypertension (systolic blood pressure 180 mmHg) was induced in rats by constricting one renal artery with a silver clip (two-kidney, one clip hypertension; 2KIC). Blood pressure, plasma renin activity (PRA) and body weight were measured for 35 days after clipping. Plasma sodium concentration and carcass sodium content were measured at the conclusion of the experiment. To determine the relationship between sodium intake, PRA and the development of severe hypertension, half of the rats were given a normal diet and water to drink; the other half were given a low sodium diet and 0.9% saline to drink. 2. In both experiments, two patterns of responses were observed. Group (1) had reduced growth rate, and marked elevation of PRA. Some, but not all of these animals had histological evidence of malignant nephrosclerosis in the untouched kidney. In the other group (11), weight gain was normal and PRA was normal or only slightly elevated. 3. Group 1 animals drinking saline, had raised carcass sodium levels, whereas those drinking water had no increase in carcass sodium. 4. The results confirm that hypertension in the 2KIC model is not always associated with a raised PRA. 5. The coexistence of a raised PRA and increased total body sodium suggests that the PRA does not rise as a result of sodium depletion in this model.