Systemic and regional haemodynamic effects of renal denervation in spontaneously hypertensive rats

Systemic and regional haemodynamic effects of renal denervation were evaluated in adult (six-month-old) male spontaneously hypertensive rats (SHR) using the Fick procedure and electromagnetic flowmetry technique. Renal denervation (bilateral, 10% phenol in ethanol), performed five to eight days before the experiment, resulted in a significant decrease (-12%) in arterial pressure in conscious SHR (denervated = 182 +/- 4 versus sham = 207 +/- 8 mmHg, P less than 0.05) that was associated with a reduction in total peripheral resistance (TPR: denervated = 1.83 +/- 0.19 versus sham = 2.78 +/- 0.29 mmHg/ml/min, P less than 0.05) and an increase in cardiac output (denervated = 106 +/- 10 versus sham = 80 +/- 9 ml/min, P less than 0.05). Heart rate was not different between the two groups. Renal, hindquarter and superior mesenteric blood flows, determined under pentobarbital anaesthesia, of denervated SHR were not significantly different from sham values. Renal vascular resistance (mmHg/ml/min) was substantially reduced (-39%) in the denervated SHR (denervated = 25.1 +/- 1.86 versus sham = 41.1 +/- 3.48, P less than 0.01), but vascular resistances in the hindquarter and superior mesenteric beds were not reduced significantly. In this preparation TPR was reduced 32% in denervated SHR. The data demonstrate that renal denervation in adult SHR proves an antihypertensive vasodilator-like effect related to a decrease in TPR with increased cardiac output. The reduction in renal vascular resistance in denervated SHR may produce a major contribution to decreased TPR. Other beds may also contribute to the decrease in TPR, although to a lesser extent, since the decrease in TPR cannot be fully accounted for by decreased renal vascular resistance.