RENAL PERFUSION-PRESSURE AND RENIN SECRETION IN BILATERALLY RENAL DENERVATED SHEEP

To further investigate the influence of renal nerves on renin secretio n, the renin secretion responses to step reductions of renal perfusion pressure (RPP) were studied in conscious sheep with innervated kidney s (n = 5) and with bilaterally denervated kidneys (n = 5). The average basal level of RPP in sheep with denervated kidneys (82 +/- 4 mmHg; 1 mmHg = 133.3 Pa) was similar to that in sheep with innervated kidneys (83 +/- 3 mmHg). RPP was reduced in four sequential 15-min steps, to a final level of 54 +/- 2 mmHg in sheep with innervated kidneys and to 57 +/- 1 mmHg in denervated sheep. The renin secretion rate was incre ased as RPP was reduced in sheep with innervated kidneys. Baseline per ipheral plasma renin activity was reduced and there was almost no resp onse of renin secretion rate to reduction of RPP in sheep with denerva ted kidneys. Also, baseline renal blood flow, urine flow rate, sodium excretion rate, and potassium excretion rate were higher in sheep with denervated kidneys than those with innervated kidneys. Baseline plasm a angiotensin II was similar in both groups of sheep. As RPP was decre ased, plasma angiotensin II was increased in sheep with innervated kid neys, but was not significantly altered in sheep with denervated kidne ys. Plasma atrial natriuretic factor was unaltered by either reduction of RPP or renal denervation. In conclusion, hormonal factors, such as angiotensin II and atrial natriuretic factor, do not account for the dramatic suppression of renin secretion in response to the reduction o f RPP in sheep with bilateral renal denervation. Penal nerves are a ne cessary component in the control of renin secretion during reduction o f RPP and may contribute to the regulation of baseline plasma renin ac tivity and sodium excretion rate in conscious ewes.