Mechanisms for Renal Blood Flow Control Early in Diabetes as Revealed by Chronic Flow Measurement and Transfer Function Analysis

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.

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Estimation of Arterial Mechanical Properties from Aortic and Tonometric Arterial Pressure Waveforms

Methods of Information in Medicine ◽

10.1055/s-0038-1636862 ◽

1997 ◽

Vol 36 (04/05) ◽

pp. 250-253 ◽

Cited By ~ 9

Author(s):

M. Sugimachi ◽

T. Kawada ◽

T. Shishido ◽

N. Matsumoto ◽

J. Alexander ◽

...

Keyword(s):

Mechanical Properties ◽

Transfer Function ◽

Arterial Pressure ◽

Flow Measurement ◽

Function Analysis ◽

Aortic Pressure ◽

Elastic Tube ◽

Windkessel Model ◽

Transfer Function Analysis ◽

Model Transfer

Abstract:Although arterial mechanical properties have been evaluated using arterial input impedance, the relative difficulty in accurate flow measurement made the value of impedance somewhat limited. To develop an alternative method to evaluate arterial mechanical properties, we analyzed the aortic pressure (AoP)-radial arterial pressure (RAP) relationship because of relative ease in obtaining peripheral pressure waveform by tonometry. In 8 patients we simultaneously recorded aortic root and radial arterial pressure waveforms. We calculated the transfer function from AoP to RAP. We then fitted the transfer function to a model of a lossless uniform elastic tube terminated with a modified Windkessel model. The fact that the model transfer function predicted AoP from RAP waveform with considerable accuracy indicated that the model represented the arterial mechanical properties well. We conclude that we can estimate the arterial mechanical properties by the pressure-pressure transfer function analysis.

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Dynamic relationship between sympathetic nerve activity and renal blood flow: a frequency domain approach

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.2001.281.1.r206 ◽

2001 ◽

Vol 281 (1) ◽

pp. R206-R212 ◽

Cited By ~ 32

Author(s):

Sarah-Jane Guild ◽

Paul C. Austin ◽

Michael Navakatikyan ◽

John V. Ringwood ◽

Simon C. Malpas

Keyword(s):

Blood Flow ◽

Transfer Function ◽

Renal Blood Flow ◽

Sympathetic Nerve ◽

Sympathetic Nerve Activity ◽

Nerve Activity ◽

Pass Filter ◽

Low Pass Filter ◽

Dynamic Relationship ◽

Transfer Function Analysis

Blood pressure displays an oscillation at 0.1 Hz in humans that is well established to be due to oscillations in sympathetic nerve activity (SNA). However, the mechanisms that control the strength or frequency of this oscillation are poorly understood. The aim of the present study was to define the dynamic relationship between SNA and the vasculature. The sympathetic nerves to the kidney were electrically stimulated in six pentobarbital-sodium anesthetized rabbits, and the renal blood flow response was recorded. A pseudo-random binary sequence (PRBS) was applied to the renal nerves, which contains equal spectral power at frequencies in the range of interest (<1 Hz). Transfer function analysis revealed a complex system composed of low-pass filter characteristics but also with regions of constant gain. A model was developed that accounted for this relationship composed of a 2 zero/4 pole transfer function. Although the position of the poles and zeros varied among animals, the model structure was consistent. We also found the time delay between the stimulus and the RBF responses to be consistent among animals (mean 672 ± 22 ms). We propose that the identification of the precise relationship between SNA and renal blood flow (RBF) is a fundamental and necessary step toward understanding the interaction between SNA and other physiological mediators of RBF.

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Renal blood flow control by tubuloglomerular feedback (TGF) in normal and spontaneously hypertensive rats — a role for dopamine and adenosine

Klinische Wochenschrift ◽

10.1007/bf01649321 ◽

1991 ◽

Vol 69 (13) ◽

pp. 587-596 ◽

Cited By ~ 7

Author(s):

D. A. Häberle ◽

B. Königbauer ◽

M. Kawabata ◽

Y. Ushiogi

Keyword(s):

Blood Flow ◽

Flow Control ◽

Renal Blood Flow ◽

Spontaneously Hypertensive Rats ◽

Tubuloglomerular Feedback ◽

Hypertensive Rats ◽

Spontaneously Hypertensive ◽

Blood Flow Control

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Transfer function analysis for the assessment of cerebral autoregulation using spontaneous oscillations in blood pressure and cerebral blood flow

Medical Engineering & Physics ◽

10.1016/j.medengphy.2014.02.001 ◽

2014 ◽

Vol 36 (5) ◽

pp. 563-575 ◽

Cited By ~ 30

Author(s):

Aisha S.S. Meel-van den Abeelen ◽

Arenda H.E.A. van Beek ◽

Cornelis H. Slump ◽

Ronney B. Panerai ◽

Jurgen A.H.R. Claassen

Keyword(s):

Blood Pressure ◽

Blood Flow ◽

Cerebral Blood Flow ◽

Transfer Function ◽

Cerebral Autoregulation ◽

Function Analysis ◽

Transfer Function Analysis ◽

Spontaneous Oscillations

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Influence of controlled breathing patterns on cerebrovascular autoregulation and cardiac baroreceptor sensitivity

Clinical Science ◽

10.1042/cs20030194 ◽

2004 ◽

Vol 106 (2) ◽

pp. 155-162 ◽

Cited By ~ 24

Author(s):

Penelope J. EAMES ◽

John F. POTTER ◽

Ronney B. PANERAI

Keyword(s):

Blood Pressure ◽

Blood Flow ◽

Cerebral Blood Flow ◽

Transfer Function ◽

Respiratory Rate ◽

Function Analysis ◽

Step Response ◽

Arterial Blood ◽

Transfer Function Analysis ◽

Controlled Breathing

Transfer function analysis has become one of the main techniques to study the dynamic relationship between cerebral blood flow and arterial blood pressure, but the influence of different respiratory rates on cerebral blood flow has not been fully investigated. In 14 healthy volunteers, middle cerebral artery blood flow velocity, recorded using transcranial Doppler ultrasound, non-invasive beat-to-beat Finapres blood pressure, ECG and end-tidal CO2 (PETCO2) levels were recorded with subjects resting supine and breathing spontaneously or at controlled rates of 6, 10 and 15 breaths/min. Transfer function analysis and impulse and step responses were computed at each respiratory rate. PETCO2 levels tended to fall slightly during paced respiration, especially at 15 breaths/min. Controlled breathing rates did not alter transfer function analysis in the frequency range below 0.08 Hz but, above this frequency, the coherence function contained significant peaks corresponding to the respiratory frequencies. The impulse response was similar at all breathing rates, but the step response was characteristic of more efficient autoregulation with reduced PETCO2 levels associated with increasing respiratory rate. The effects of breathing rate and rhythmicity and PETCO2 must be considered in studies of cerebral autoregulation.

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Continuously measured renal blood flow does not increase in diabetes if nitric oxide synthesis is blocked

AJP Renal Physiology ◽

10.1152/ajprenal.00004.2008 ◽

2008 ◽

Vol 295 (5) ◽

pp. F1449-F1456 ◽

Cited By ~ 16

Author(s):

Tracy D. Bell ◽

Gerald F. DiBona ◽

Rachel Biemiller ◽

Michael W. Brands

Keyword(s):

Nitric Oxide ◽

Blood Flow ◽

Renal Blood Flow ◽

Function Analysis ◽

Control Period ◽

Power Spectra ◽

Tubuloglomerular Feedback ◽

Left Renal Artery ◽

Renal Vasculature ◽

Transfer Function Analysis

This study used 16 h/day measurement of renal blood flow (RBF) and arterial pressure (AP) to determine the role of nitric oxide (NO) in mediating the renal vasodilation caused by onset of type 1 diabetes. The AP and RBF power spectra were used to determine the autoregulatory efficiency of the renal vasculature. Rats were instrumented with artery and vein catheters and a Transonic flow probe on the left renal artery and were divided randomly into four groups: control (C), diabetes (D), control plus nitro-l-arginine methyl ester (l-NAME; CL), and diabetes plus l-NAME (DL). Mean AP averaged 90 ± 1 and 121 ± 1 mmHg in the D and DL groups, respectively, during the control period, and RBF averaged 5.9 ± 1.2 and 5.7 ± 0.7 ml/min, respectively. Respective C and CL groups were not different. Onset of diabetes (streptozotocin 40 mg/kg iv) in D rats increased RBF gradually, but it averaged 55% above control by day 14. In DL rats, on the other hand, RBF remained essentially constant, tracking with RBF in the nondiabetic C and CL groups for the 2-wk period. Diabetes did not change mean AP in any group. Transfer function analysis revealed impaired dynamic autoregulation of RBF overall, including the frequency range of tubuloglomerular feedback (TGF), and l-NAME completely prevented those changes as well. These data strongly support a role for NO in causing renal vasodilation in diabetes and suggest that an effect of NO to blunt RBF autoregulation may play an important role.

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The Effect of Sevoflurane on Dynamic Cerebral Blood Flow Autoregulation Assessed by Spectral and Transfer Function Analysis

Anesthesia & Analgesia ◽

10.1213/01.ane.0000189056.96273.48 ◽

2006 ◽

Vol 102 (2) ◽

pp. 552-559 ◽

Cited By ~ 32

Author(s):

Yojiro Ogawa ◽

Ken-ichi Iwasaki ◽

Shigeki Shibata ◽

Jitsu Kato ◽

Setsuro Ogawa ◽

...

Keyword(s):

Blood Flow ◽

Cerebral Blood Flow ◽

Transfer Function ◽

Function Analysis ◽

Transfer Function Analysis ◽

Cerebral Blood Flow Autoregulation

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Blood pressure-renal blood flow relationships in conscious angiotensin II- and phenylephrine-infused rats

AJP Renal Physiology ◽

10.1152/ajprenal.00111.2013 ◽

2013 ◽

Vol 305 (7) ◽

pp. F1074-F1084 ◽

Cited By ~ 16

Author(s):

Aaron J. Polichnowski ◽

Karen A. Griffin ◽

Jianrui Long ◽

Geoffrey A. Williamson ◽

Anil K. Bidani

Keyword(s):

Blood Pressure ◽

Blood Flow ◽

Renal Blood Flow ◽

Function Analysis ◽

Heart Beat ◽

Ang Ii ◽

Sprague Dawley ◽

Renal Vasculature ◽

Conscious Rats ◽

Transfer Function Analysis

Chronic ANG II infusion in rodents is widely used as an experimental model of hypertension, yet very limited data are available describing the resulting blood pressure-renal blood flow (BP-RBF) relationships in conscious rats. Accordingly, male Sprague-Dawley rats ( n = 19) were instrumented for chronic measurements of BP (radiotelemetry) and RBF (Transonic Systems, Ithaca, NY). One week later, two or three separate 2-h recordings of BP and RBF were obtained in conscious rats at 24-h intervals, in addition to separate 24-h BP recordings. Rats were then administered either ANG II ( n = 11, 125 ng·kg−1·min−1) or phenylephrine (PE; n = 8, 50 mg·kg−1·day−1) as a control, ANG II-independent, pressor agent. Three days later the BP-RBF and 24-h BP recordings were repeated over several days. Despite similar increases in BP, PE led to significantly greater BP lability at the heart beat and very low frequency bandwidths. Conversely, ANG II, but not PE, caused significant renal vasoconstriction (a 62% increase in renal vascular resistance and a 21% decrease in RBF) and increased variability in BP-RBF relationships. Transfer function analysis of BP (input) and RBF (output) were consistent with a significant potentiation of the renal myogenic mechanism during ANG II administration, likely contributing, in part, to the exaggerated reductions in RBF during periods of BP elevations. We conclude that relatively equipressor doses of ANG II and PE lead to greatly different ambient BP profiles and effects on the renal vasculature when assessed in conscious rats. These data may have important implications regarding the pathogenesis of hypertension-induced injury in these models of hypertension.

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