Effect of protein intake on the autoregulation of renal blood flow

Autoregulatory ability was evaluated in male Sprague-Dawley rats (200-250 g) fed either low protein (LP, 6%), high protein (HP, 50%), or standard rat chow (CON) for 2 wk. Renal perfusion pressure (RPP) was first raised above normal by bilateral ligation of the carotid arteries. LP rats exhibited normal autoregulatory behavior between 130 and 100 mmHg, whereas autoregulation in HP rats was impaired (autoregulation factor 100-130; HP 0.86 ± 0.16, LP 0.38 ± 0.07, and CON 0.39 ± 0.04). Autoregulation studies were repeated in HP- and LP-fed rats after administration of the cyclooxygenase inhibitors, meclofenamate and piroxicam. Cyclooxygenase inhibition did not significantly affect base-line hemodynamics but did restore the ability of the HP rat to autoregulate renal blood flow (RBF) at high RPP. (Autoregulation factor between 100 and 130 mmHg; HP 0.29 ± 0.10, LP 0.19 ± 0.07, P, NS.) Thus an HP diet resulted in impaired autoregulation of RBF at high RPP, an effect that appears to be mediated by excessive production of vasodilatory prostaglandins.