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1 Department of Biomedical Engineering, SUNY @ Stony Brook, Stony Brook, NY, USA
2 Department of Nephrology, Chang Gung Memorial Hospital, Taiwan
3 Department of Molecular Pharmacology,Physiology, and Biotechnology, Brown University, Providence, RI, USA
4 Department of Physiology & Biophysics, University of South Florida, Tampa, FL, USA
* To whom correspondence should be addressed. E-mail: ki.chon{at}sunysb.edu.
We have previously shown that there are two oscillating components in spontaneously fluctuating single nephron blood flow obtained from Sprague-Dawley rats. The slow oscillation (20-30 mHz) is mediated by tubuloglomerular feedback (TGF) while the fast oscillation (100 mHz) is probably related to spontaneous myogenic activity. The fast oscillation is rarely detected in spontaneous tubular pressure because of its small magnitude and the fact that tubular compliance filters pressure waves. We detected the myogenic oscillation superimposed on the TGF-mediated oscillation when ambient tubular flow was interrupted. Two well-defined peaks are present in the mean power spectrum of stop flow pressure centering at 25 and 100 mHz (n=13) in addition to a small peak at 125-130 mHz. Bispectral analysis indicates that two of these oscillations (30 and 100mHz) interact nonlinearly to produce the third oscillation at 125-130 mHz. The presence of nonlinear interactions between TGF and myogenic oscillations indicates that estimates of the relative contribution of each of these mechanisms in renal autoregulation need to account for this interaction. The magnitude of myogenic-oscillations were considerably smaller in the stop flow pressure measured from spontaneously hypertensive rats (SHR, n=13); consequently, nonlinear interactions were not observed with bispectral analysis. Reduced augmentation of the myogenic oscillations in SFP of SHR might account for the failure in detecting nonlinear interactions in SHR.
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