Supersensitivity to NE alters renal function of chronically denervated rat kidneys

The effect of norepinephrine (NE) infusion (10, 100, and 330 ng/min, iv) on renal blood flow (RBF), glomerular filtration rate (GFR), urine flow, and sodium excretion was studied during ganglionic blockade in Inactin-anesthetized Wistar rats with one kidney innervated and the contralateral kidney denervated 7-10 days before the experiment. During the NE infusions, steady-state mean arterial pressure was 73 +/- 3, 91 +/- 5, and 117 +/- 2 mmHg, whereas plasma NE concentration averaged 3.9 +/- 1.2, 26.4 +/- 3.2, and 78.1 +/- 4.8 pmol/ml, respectively. At the lowest dose, RBF and GFR were decreased significantly in both kidneys but were significantly lower in the denervated kidneys than in the innervated kidneys. Urine flow and total and fractional sodium excretion increased significantly from the innervated kidneys but not from the denervated kidneys during the 100 and 330 ng/min infusion of NE. When renal perfusion pressure was controlled at the level found after ganglionic blockade, RBF and GFR decreased significantly in both kidneys but to a greater extent in the denervated kidneys at all doses of NE. Urine flow and total and fractional sodium excretion decreased significantly from the denervated kidneys at all doses of NE but decreased from the innervated kidneys only at the highest dose. These results indicate that in chronically denervated kidneys both tubular and vascular responses to NE are altered. The data support the conclusion that denervation supersensitivity can significantly alter renal responses to increased plasma concentration of NE.