A physiological role for pressure-dependent renin release in long-term blood pressure control

The relationship between pressure-dependent renin release and long-term blood pressure was studied in 14 conscious dogs on a normal salt diet. Stimulus-response curves were obtained by a controlled reduction of renal artery pressure in 5 or 10 mm Hg steps down to 70 mm Hg. Pressure-dependent renin release was characterized by a threshold pressure, a plateau above threshold pressure, and a steep slope below the threshold pressure. In each dog long-term blood pressure was higher than threshold pressure. Threshold pressure and slope were found to describe more than 90% of long-term blood pressure variability between conscious dogs. The following findings suggest that an on-off switch of pressure-dependent renin release stabilizes long-term blood pressure above the threshold pressure: (1) The intermittent activation of pressure-dependent renin release due to physiological variations in arterial blood pressure induced changes in plasma renin activity by as much as 300%. (2) The individual difference between threshold pressure and long-term blood pressure was highly dependent on the slope. (3) A systemic blockade of the renin-angiotensin system by converting-enzyme inhibition resulted in a slope-dependent fall of long-term blood pressure. (4) A spontaneous shift of threshold pressure was accompanied by equivalent changes in arterial blood pressure. Taken together, our results provide evidence for a major role of pressure-dependent renin release in the long-term control of blood pressure in conscious dogs. A chronic resetting of threshold pressure may be an important mechanism in the pathogenesis of hypertension.