Effects of tempol and candesartan on neural control of the kidney

Area of Science:

• Nephrology
• Pharmacology
• Physiology

Background:

• The role of superoxide and angiotensin II in renal function and nerve responses is not fully understood.
• Investigating the differential effects of antioxidants and AT1 receptor antagonists on renal hemodynamics is crucial.

Purpose of the Study:

• To compare the effects of tempol (antioxidant) and candesartan (AT1 receptor antagonist) on renal hemodynamics, excretory function, and renal nerve stimulation (RNS) responses.
• To determine the contribution of superoxide to angiotensin II's actions on renal function and RNS responses in lean and obese rabbits.

Main Methods:

• Comparison of tempol and candesartan administration in lean and obese rabbits under anesthesia.
• Assessment of renal blood flow (RBF), glomerular filtration rate (GFR), and sodium excretion (U(Na)V).
• Evaluation of responses to electrical stimulation of the renal nerves (RNS) and effects of drugs on these responses.

Main Results:

• Candesartan increased RBF, while tempol reduced GFR and sodium excretion. Both drugs had similar depressor effects.
• RNS reduced RBF, GFR, and U(Na)V. Candesartan blunted these RNS-induced reductions, while tempol only blunted the U(Na)V response.
• Tempol did not alter RBF or GFR responses to RNS, unlike candesartan. Effects were similar in lean and obese rabbits.

Conclusions:

• Tempol does not blunt RNS effects on renal hemodynamics, unlike candesartan, suggesting superoxide has a limited role in angiotensin II's actions on baseline renal function and RNS responses.
• The study highlights distinct mechanisms of action for tempol and candesartan on renal hemodynamics and nerve responses.
• Superoxide's contribution to endogenous angiotensin II's effects on renal hemodynamics and excretory function appears minimal under these experimental conditions.