Tubuloglomerular Feedback Signal Transduction In a Model of a Compliant Thick Ascending Limb
by
Anita T. Layton
Duke University, Department of Mathematics

We used a mathematical model to predict the impact of tubular compliance on tubuloglomerular feedback (TGF) signal

transduction in the thick ascending limb (TAL). In several previous studies, we used a mathematical model that represented the TAL as

a rigid tube. That model predicts that TGF signal transduction by the TAL is a generator of nonlinearities: if a sinusoidal oscillation

is added to constant intratubular flow, the NaCl concentration alongside the macula densa will be nonsinusoidal owing to an

accumulation of harmonics. We have hypothesized that complexity found in power spectra based on in vivo time series of key TGF

variables arises in part from those harmonics and that nonlinearities in TGF-mediated oscillations may result in increased

NaCl delivery to the distal nephron. To address the concern that a more realistic TAL would damp harmonics, we have conducted

simulations in a model TAL that has compliant walls and thus a tubular radius that depends on transmural pressure. These

simulations predict that compliant TAL walls do not damp, but instead, intensify the harmonics.

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Date received: April 16, 2008