AJP - Regulatory, Integrative and Comparative Physiology, Vol 273, Issue 4 1414-R1420, Copyright © 1997 by American Physiological Society

ARTICLES

Reduced proximal reabsorption resets tubuloglomerular feedback in euvolemic rats

S. C. Thomson, V. Vallon and R. C. Blantz
Department of Medicine, University of California and Veterans Affairs Medical Center, San Diego 92161, USA.

Inhibition of renal carbonic anhydrase reduces proximal reabsorption and activates tubuloglomerular feedback (TGF). The TGF response is saturable, with highest gain focused near the natural flow rate. Therefore, any large change imposed on ambient tubular flow should reduce the TGF response to subequent flow perturbations. However, TGF tends to align with ambient flow regardless of the rate of ambient flow, suggesting that TGF resets to accommodate changes in flow while maintaining feedback efficiency. We used micropuncture and videometric flow velocitometry to test for TGF resetting in free-flowing nephrons during systemic infusion of the carbonic anhydrase inhibitor benzolamide (BNZ, 5 mg x kg(-1) x h(-1)) in euvolemic rats. Late proximal flow (V(LP)) and the fractional compensation (C) of TGF for perturbations in V(LP) were assessed repeatedly before and during BNZ. Early on, BNZ reduced C, consistent with TGF saturation. Over the next 45-60 min, V(LP) increased gradually by approximately 5 nl/min as C recovered to pre-BNZ levels. BNZ also increased V(LP) by approximately 5 nl/min when TGF was rendered inoperative by intratubular wax block, but this increase occurred rapidly. These data demonstrate rightward resetting of TGF during reduced proximal reabsorption.

This article has been cited by other articles:

				C. M. Miracle, T. Rieg, H. Mansoury, V. Vallon, and S. C. Thomson Ornithine decarboxylase inhibitor eliminates hyperresponsiveness of the early diabetic proximal tubule to dietary salt Am J Physiol Renal Physiol, October 1, 2008; 295(4): F995 - F1002. [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]

				J. Satriano, L. Wead, A. Cardus, A. Deng, G. R. Boss, S. C. Thomson, and R. C. Blantz Regulation of ecto-5'-nucleotidase by NaCl and nitric oxide: potential roles in tubuloglomerular feedback and adaptation Am J Physiol Renal Physiol, November 1, 2006; 291(5): F1078 - F1082. [Abstract] [Full Text] [PDF]

				S. C. Thomson, A. Deng, N. Komine, J. S. Hammes, R. C. Blantz, and F. B. Gabbai Early diabetes as a model for testing the regulation of juxtaglomerular NOS I Am J Physiol Renal Physiol, October 1, 2004; 287(4): F732 - F738. [Abstract] [Full Text] [PDF]

				S. C. Thomson, V. Vallon, and R. C. Blantz Kidney function in early diabetes: the tubular hypothesis of glomerular filtration Am J Physiol Renal Physiol, January 1, 2004; 286(1): F8 - F15. [Abstract] [Full Text] [PDF]

				D. R. Oldson, L. C. Moore, and H. E. Layton Effect of sustained flow perturbations on stability and compensation of tubuloglomerular feedback Am J Physiol Renal Physiol, November 1, 2003; 285(5): F972 - F989. [Abstract] [Full Text] [PDF]

				E. Turkstra, B. Braam, and H. A. Koomans Normal TGF Responsiveness During Chronic Treatment With Angiotensin-Converting Enzyme Inhibition : Role of AT1 Receptors Hypertension, November 1, 2000; 36(5): 818 - 823. [Abstract] [Full Text] [PDF]

				H. E. Layton, E. B. Pitman, and L. C. Moore Limit-cycle oscillations and tubuloglomerular feedback regulation of distal sodium delivery Am J Physiol Renal Physiol, February 1, 2000; 278(2): F287 - F301. [Abstract] [Full Text] [PDF]