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Articles in PresS, published online ahead of print August 8, 2001
Am J Physiol Renal Physiol, 10.1152/ajprenal.0186.2001
Submitted on June 18, 2001
Accepted on July 20, 2001
1 CNRS UMR 5014, Universite Claude Bernard Lyon 1, Lyon, France
* To whom correspondence should be addressed. E-mail: barres{at}univ-lyon1.fr.
These experiments examined whether the conscious sinoaortic denervated (SAD) rat, owing to its high spontaneous arterial pressure (AP) variability, might represent a model for renal blood flow (RBF) autoregulation studies. In 8 SAD and 6 baroreceptor intact rats, AP and RBF were recorded (1-h periods) before and after furosemide (10 mg/kg followed by 10 mg/kg/h iv) administration. In control conditions, AP variability was markedly enhanced in SAD rats (coefficient of variation: 16.0 ± 1.2% vs. 5.4 ± 0.5% in intact rats) whereas RBF variability was only slightly increased (8.7 ± 0.6 vs. 6.1 ± 0.5% in intact rats), suggesting buffering by autoregulatory mechanisms. In SAD but not in intact rats, the AP-RBF relationships could be modeled with a 4-parameter sigmoid Weibull equation (r2 = 0.24 ± 0.07, 3,600 data pairs in each rat), allowing for estimation of an autoregulatory plateau (10.1 ± 0.7 ml/min) and a lower limit of RBF autoregulation (PLL = 93 ± 6 mmHg, defined as AP at RBF 5% below the plateau). After furosemide treatment, autoregulation curves (r2 = 0.49 ± 0.07) were downward (plateau = 8.6 ± 0.8 ml/min) and rightward (PLL = 102 ± 5 mmHg) shifted in SAD rats. In 5 of 6 intact rats, PLL became measurable (104 ± 1 mmHg), albeit with a limited accuracy (r2 = 0.09 ± 0.03). In conclusion, the conscious SAD rat offers the possibility to describe RBF autoregulation curves under dynamic unforced conditions. The tubuloglomerular feedback and myogenic mechanisms cooperate in setting PLL and thus in stabilizing RBF during spontaneous depressor episodes.
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