Sympathetic nervous system and blood-pressure control in essential hypertension.

In normotensive subjects an inverse correlation was observed between an index of sympathetic nervous activity (the plasma-noradrenaline concentration during physical exercise) and reactivity to exogenous noradrenaline. This relationship was invariably disturbed in age-matched patients with essential hypertension. Multiple-regression analysis revealed a highly significant correlation between the combination of both factors and the height of mean arterial blood-pressure (r=0.91). The findings suggest that sympathetic nervous activity and pressor response to noradrenaline together form an important determinant of the arterial blood-pressure level. An inverse relationship could be demonstrated between plasma-renin concentration and pressor response to angiotensin II in normotensives, and this relationship was unchanged in hypertensive patients. Therefore angiotensin II does not appear to contribute directly to high blood-pressure.