False-negative saralasin responses in renovascular hypertension

Blood pressure responses to the infusion of saralasin and plasma renin levels were measured in 31 hypertensive patients following preparation with frusemide. Five patients had unilateral renal artery stenosis, with renal vein ratios lateralising strongly to the affected side. Saralasin produced depressor responses in 3 of these but failed to evoke significant effects in the other 2, despite the fact that in both cases hypertension was subsequently alleviated by renal bypass surgery. A further period of more severe sodium depletion increased plasma renin levels and the depressor effect of saralasin, but did not help to differentiate renal artery stenosis from other forms of hypertension.