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.
