Acute pressure-natriuresis relationship following withdrawal of chronic noradrenaline infusion

1. Pathological changes to the kidney, such as vascular remodelling, have been found in several models of hypertension and may contribute to the maintenance of hypertension or confer susceptibility to redeveloping hypertension after the original prohypertensive stimulus is withdrawn. 2. To investigate whether noradrenaline-induced hypertension induces persistent, functionally important changes to the kidney, the acute pressure-natriuresis relationship was characterized in anaesthetized rats under controlled neural and hormonal conditions following chronic (14 days) intravenous infusion of noradrenaline (48 μg/kg per h) or vehicle (0.04 mg/mL ascorbic acid and 0.156 mg/mL NaH₂PO₄·2H₂O in 10 IU/mL heparinized saline). 3. Conscious mean arterial pressure was significantly elevated by infusion of noradrenaline at 48 μg/kg per h (+10 ± 2 mmHg at Day 14; P < 0.01 vs vehicle group). The acute relationships between arterial pressure and renal blood flow, glomerular filtration rate, Na ⁺ excretion and urine flow were not significantly different between the noradrenaline- and vehicle-infused rats immediately after termination of noradrenaline infusion. 4. In summary, chronic intravenous noradrenaline infusion did not cause persistent changes in renal function, indicating that, in contrast with many models of hypertension, this model does not induce underlying prohypertensive changes to the kidney.