High-NaCl intake impairs dynamic autoregulation of renal blood flow in ANG II-infused rats

Saeed A, DiBona GF, Marcussen N, Guron G. High-NaCl intake impairs dynamic autoregulation of renal blood flow in ANG II-infused rats. Am J Physiol Regul Integr Comp Physiol 299: R1142-R1149, 2010. First published August 18, 2010; doi:10.1152/ajpregu.00326.2010.-The aim of this study was to investigate dynamic autoregulation of renal blood flow (RBF) in ANG II-infused rats and the influence of high-NaCl intake. Sprague-Dawley rats received ANG II (250 ng.kg(-1).min(-1) sc) or saline vehicle (sham) for 14 days after which acute renal clearance experiments were performed during thiobutabarbital anesthesia. Rats (n = 8-10 per group) were either on a normal (NNa; 0.4% NaCl)-or high (HNa; 8% NaCl)-NaCl diet. Separate groups were treated with 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (tempol; 1 M in drinking water). Transfer function analysis from arterial pressure to RBF in the frequency domain was used to examine the myogenic response (MR; 0.06-0.09 Hz) and the tubuloglomerular feedback mechanism (TGF; 0.03-0.06 Hz). MAP was elevated in ANG II-infused rats compared with sham groups (P < 0.05). RBF in ANG II HNa was reduced vs. sham NNa and sham HNa (6.0 +/- 0.3 vs. 7.9 +/- 0.3 and 9.1 +/- 0.3 ml.min(-1).g kidney wt(-1), P < 0.05). transfer function gain in ANG II HNa was significantly elevated in the frequency range of the MR (1.26 +/- 0.50 dB, P < 0.05 vs. all other groups) and in the frequency range of the TGF (-0.02 +/- 0.50 dB, P < 0.05 vs. sham NNa and sham HNa). Gain values in the frequency range of the MR and TGF were significantly reduced by tempol in ANG II-infused rats on HNa diet. In summary, the MR and TGF components of RBF autoregulation were impaired in ANG II HNa, and these abnormalities were attenuated by tempol, suggesting a pathogenetic role for superoxide in the impaired RBF autoregulatory response.