[Role of the renin-angiotensin system in arterial hypertension with aortic coarctation in young adults].

The renin-angiotensin system (RAS) was evaluated in 7 hypertensives with pure isthmic coarctation of the aorta. RAS was studied under basal conditions, standing, after saralasine (a specific angiotensin II antagonist) and after acebutolol (a cardioselective beta-blocker and an inhibitor of renin secretion). Plasma volume was measured by radio isotopic methods and cardiac catheterisation was performed to assess the pressure gradient across the coarctation. On a normal salt diet on orthostatism, plasma renin activity (PRA) was increased in 5 patients and normal in the other 2. After moderate salt depletion, saralasine injection caused a significant fall in diastolic blood pressure (89,2 +/- 4,4 to 77,3 +/- 6,6 mmHg; p < 0,02) with an associated rise in PRA (5,7 +/- 4,4 to 17,1 +/- 9,1; p < 0,01). There was no correlation between these two parameters or their variations. The test was negative in two patients. The antihypertensive effect of acebutolol was moderate due partly to the absence of salt depletion. Inhibition of renin secretion by acebutolol was significant (4,7 to 1,95 +/- 1,10 ng AI/ml/h; p < 0,02) but did not correlate with variations of arterial blood pressure. There was no correlation between the antihypertensive effect of saralasine and acebutolol (R = 0,51). Plasma volume (n = 5) was almost always increased (47,15 +/- 5,4 ml/kg). No correlations were observed between the different levels of PRA, plasma volume, and the systolic and/or diastolic gradient. In conclusion, this study underlines the limitations of isolated peripheral assessment of PRA and the acebutolol test. On the other hand, the effectiveness of saralasine, a specific RAS antagonist, and the demonstration of the effective participation of this system associated with the usual increase in plasma volume, seems to liken coarctation of the aorta to the single kidney Goldblatt experimental model.