Asymmetry of tubuloglomerular feedback effector mechanism with
respect to ambient tubular flow.
Thomson, Scott, Volker Vallon, and Roland C. Blantz.
Division of Nephrology-Hypertension, Dept of Medicine, University
of California San Diego and San Diego Veterans Affairs Medical
Center, San Diego California 92161
APStracts 3:0150F, 1996.
The contribution of pre-glomerular resistance changes to the
tubuloglomerular feedback (TGF) effector response was evaluated by
micropuncture in hydropenic rats. Studies were performed in free
-flowing nephrons to compare the fractional compensation (C) for
perturbations in late proximal flow (VLP) with associated changes in
glomerular capillary hydrostatic pressure (PGC). VLP was monitored by
a non-invasive optical technique, and PGC by direct capillary
micropuncture. Data were employed in conjunction with a model of
glomerular filtration to analyze the TGF effector mechanism. C varied
with the applied perturbation (VH), showing a single peak near the
natural operating point. In contrast, the effect of TGF on PGC was
asymmetric about the operating point, such that PGC was sensitive
only to large positive perturbations. The model predicts that changes
in pre-glomerular resistance account for only a small fraction of the
integrated TGF response to small disturbances in the ambient state of
the nephron, but for a greater share of the response to larger
increments in flow. The TGF response in hydropenic rats is mediated
by both pre- and post-glomerular vascular elements.
Received 2 February 1996; accepted in final form 8 August 1996.
APS Manuscript Number F36-6.
Article publication pending Am. J. Physiol. (Renal Fluid Electrolyte
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 29 August 1996