The relative roles of sodium and renin in the hypertension of renal disease. An assessment based on the response to frusemide and propranolol.
Twenty-seven patients with hypertension and varying degrees of renal failure were studied before and during the administration of frusemide. In 15 patients studies were repeated following the addition of propranolol. Mean exchangeable sodium was increased before the introduction of frusemide or propranolol in patients with azotemia, possibly due in part to the administration of other antihypertensive drugs, and was reduced to normal during frusemide treatment increasing slightly but significantly following the addition of propranolol. Blood pressure fell significantly with frusemide but there was no further significant fall with propranolol. The relationship of change in blood pressure to change in exchangeable sodium with frusemide did not reach significance. There was no relationship between changes in blood pressure and changes in plasma renin activity with frusemide, suggesting that the blood pressure response to frusemide is not limited by the rise in renin. The fall in blood pressure following the addition of propranolol was proportional to the dose of the drug but inversely proportional to the change in renin suggesting that renin levels are to some extent determined by the blood pressure response to propranolol rather than themselves determining that response. Serum creatinine was significantly increased during treatment with frusemide probably due to a combination of the effects of sodium depletion and the natural progression of the underlying renal disease rather than to nephrotoxicity. The further slight increase in serum creatinine following the addition of propranolol is in keeping with the reported effect of this drug on renal blood flow and glomerular filtration rate in patients without renal disease.