HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 286/6/F1136    most recent 00401.2003v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via ISI Web of Science (13) Citing Articles via Google Scholar Google Scholar Articles by Griffin, K. A. Articles by Bidani, A. K. Search for Related Content PubMed PubMed Citation Articles by Griffin, K. A. Articles by Bidani, A. K.

Effects of calcium channel blockers on "dynamic" and "steady-state step" renal autoregulation

¹Department of Internal Medicine, Loyola University Medical Center, and Edward Hines, Jr. Veterans Affairs Hospital, Maywood 60153; ²Department of Electrical and Computer Engineering, Illinois Institute of Technology, Chicago, Illinois 60616-3793; and ³Department of Pharmacology and Therapeutics, University of Calgary, Calgary, Alberta, Canada T2N 4N1

Submitted 12 November 2003 ; accepted in final form 23 February 2004

Renal autoregulation (AR) mechanisms provide the primary protection against transmission of systemic pressures and hypertensive renal damage. However, the relative merits of the "step" change vs. "dynamic" methods for the assessment of AR capacity remain controversial. The effects of 48–72 h of orally administered amlodipine (L-type) and mibefradil (T-type) calcium channel blockers (CCBs) on step and dynamic AR in Sprague-Dawley rats were compared. Both CCBs significantly impaired "steady-state step" AR (autoregulatory indexes = 0.5 vs. 0.1 in controls, P < 0.05; n = 9–10/group). By contrast, dynamic AR compensation in separate conscious rats (n = 12) was not significantly altered by either amlodipine (n = 10) or mibefradil (n = 6; fractional gain in admittance 0.4–0.5 in all groups at frequencies in the range of 0.0025–0.025 Hz). However, both CCBs tended to attenuate the myogenic resonance peak along with shifting it to a significantly slower frequency (P < 0.001) during dynamic AR, but no consistent effects were observed on the tubuloglomerular feedback resonance peak. While the reasons for the insensitivity of dynamic vs. steady-state step AR capacity estimates to CCBs remain to be established, the present data indicate that dynamic AR methods may have a limited utility for assessing AR capacity but may provide potentially important insights into the operational characteristics of AR control mechanisms. A strong correlation was also observed between the average conductance and the admittance gain at the heart beat frequency (r = 0.77, P < 0.001), suggesting that such parameters may provide additional and possibly more meaningful indexes of BP transmission in conscious animals during dynamic AR.

renal hemodynamics; hypertension; myogenic response; tubuloglomerular feedback

This article has been cited by other articles:

				R. Iliescu, R. Cazan, G. R. McLemore Jr., M. Venegas-Pont, and M. J. Ryan Renal blood flow and dynamic autoregulation in conscious mice Am J Physiol Renal Physiol, September 1, 2008; 295(3): F734 - F740. [Abstract] [Full Text] [PDF]

				K. A. Griffin, M. Abu-Naser, I. Abu-Amarah, M. Picken, G. A. Williamson, and A. K. Bidani Dynamic blood pressure load and nephropathy in the ZSF1 (fa/facp) model of type 2 diabetes Am J Physiol Renal Physiol, November 1, 2007; 293(5): F1605 - F1613. [Abstract] [Full Text] [PDF]

				W. A. Cupples and B. Braam Assessment of renal autoregulation Am J Physiol Renal Physiol, April 1, 2007; 292(4): F1105 - F1123. [Abstract] [Full Text] [PDF]

				A. Just Mechanisms of renal blood flow autoregulation: dynamics and contributions Am J Physiol Regulatory Integrative Comp Physiol, January 1, 2007; 292(1): R1 - R17. [Abstract] [Full Text] [PDF]

				R. Loutzenhiser, K. Griffin, G. Williamson, and A. Bidani Renal autoregulation: new perspectives regarding the protective and regulatory roles of the underlying mechanisms Am J Physiol Regulatory Integrative Comp Physiol, May 1, 2006; 290(5): R1153 - R1167. [Abstract] [Full Text] [PDF]

				N. Khosla and G. Bakris Lessons Learned from Recent Hypertension Trials about Kidney Disease Clin. J. Am. Soc. Nephrol., March 1, 2006; 1(2): 229 - 235. [Full Text] [PDF]

				S. Nathan, C. J. Pepine, and G. L. Bakris Calcium Antagonists: Effects on Cardio-Renal Risk in Hypertensive Patients Hypertension, October 1, 2005; 46(4): 637 - 642. [Abstract] [Full Text] [PDF]

				I. Abu-Amarah, A. K. Bidani, R. Hacioglu, G. A. Williamson, and K. A. Griffin Differential effects of salt on renal hemodynamics and potential pressure transmission in stroke-prone and stroke-resistant spontaneously hypertensive rats Am J Physiol Renal Physiol, August 1, 2005; 289(2): F305 - F313. [Abstract] [Full Text] [PDF]