Spontaneous renal blood flow autoregulation curves in conscious sinoaortic baroreceptor-denervated rats

Abstract

Pires, Silene L. S., Claude Julien, Bruno Chapuis, Jean Sassard, and Christian Barrè s. Spontaneous renal blood flow autoregulation curves in conscious sinoaortic baroreceptor-denervated rats. Am J Physiol Renal Physiol 282: F51-F58, 2002. First published August 8, 2001 10.1152/ajprenal.00186.2001.-These experiments examined whether the conscious sinoaortic baroreceptor-denervated (SAD) rat, owing to its high spontaneous arterial pressure (AP) variability, might represent a model for renal blood flow (RBF) autoregulation studies. In eight SAD and six baroreceptor-intact rats, AP and RBF were recorded (1-h periods) before and after furosemide (10 mg/kg followed by 10 mg ⅐ kg Ϫ1 ⅐ h Ϫ1 iv) administration. In control conditions, AP variability was markedly enhanced in SAD rats (coefficient of variation: 16.0 Ϯ 1.2 vs. 5.4 Ϯ 0.5% in intact rats), whereas RBF variability was only slightly increased (8.7 Ϯ 0.6 vs. 6.1 Ϯ 0.5% in intact rats), suggesting buffering by autoregulatory mechanisms. In SAD rats, but not in intact rats, the AP-RBF relationships could be modeled with a four-parameter sigmoid Weibull equation (r 2 ϭ 0.24 Ϯ 0.07, 3,600 data pairs/rat), allowing for estimation of an autoregulatory plateau (10.1 Ϯ 0.7 ml/min) and a lower limit of RBF autoregulation (PLL ϭ 93 Ϯ 6 mmHg, defined as AP at RBF 5% below the plateau). After furosemide treatment, autoregulation curves (r 2 ϭ 0.49 Ϯ 0.07) in SAD rats were shifted downward (plateau ϭ 8.6 Ϯ 0.8 ml/min) and rightward (PLL ϭ 102 Ϯ 5 mmHg). In five of six intact rats, PLL became measurable (104 Ϯ 1 mmHg), albeit with limited accuracy (r 2 ϭ 0.09 Ϯ 0.03). In conclusion, the conscious SAD rat offers the possibility of describing 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.arterial pressure variability; furosemide; modeling AUTOREGULATION OF TOTAL RENAL blood flow (RBF) is usually explored by measuring RBF responses to externally induced stepwise reductions of arterial pressure (AP) in both anesthetized (6,8,11,13,17,21,22) and conscious (2,4,16,18,(24)(25)(26) animals. Steady-state levels of RBF are plotted as a function of AP, which allows the drawing of autoregulation curves from which the plateau and lower pressure limit of RBF autoregulation (P LL ) are estimated. It is not known whether such information can be gained under spontaneous unforced conditions, i.e., using RBF responses to naturally occurring AP fluctuations.The conscious sinoaortic baroreceptor-denervated (SAD) rat is a well-recognized model of exaggerated AP variability, which is characterized by the spontaneous occurrence of pressor and depressor episodes of occasionally large amplitude (3,28). Recently, we have investigated in conscious SAD rats the relationships between AP variability and RBF variability (20). Although AP variability was markedly increased, RBF variability was only slightly increased, suggesting a powerful participa...

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“…A striking time-associated variability of RBF was observed at any given BP in individual rats in the present study, which has also been observed previously (58,70,81). Nevertheless, despite this variability in RBF, the BP-RBF bin analysis in the present study (Fig.…”

Renal autoregulation: new perspectives regarding the protective and regulatory roles of the underlying mechanisms

“…7, which depicts the variations in RBF and BP seen over a 2-h period in a conscious, unrestrained rat. Similar observations are reported by other laboratories (120,123,142,143). Such temporal variability may reflect the influence of neurohormonal and metabolic inputs (Fig.…”

Dynamic myogenic autoregulation in the rat kidney: a whole-organ model

“…This occurs via dilation or constriction in response to alterations in blood pressure, which incite changes in circumferential wall tension. The active myogenic response closely follows an initial passive distension, as has been observed in a multitude of experimental studies (5,11,19,26,27,30,32,39,45,58,61,63).…”

“…9B), with a non-zero gradient of flow with respect to pressure in the autoregulatory range due to the omission of TGF from the model. This corresponds well to data from the experimental scenario that most closely simulates the condition of purely myogenic renal autoregulation (45). To prevent bias, this data set was not used to determine the parameters used in the mathematical system.…”

“…8B. Pires et al (45) performed experiments to determine spontaneous renal blood flow autoregulation curves in conscious sinoaortic baroreceptor-denervated rats, inhibiting the TGF with furosemide. This is known to cause near-complete suppression of the TGF response (30,32,45,53,55,63).…”