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Efficiency of sodium transport in a model of the Thick Ascending Limb (TAL)
Author(s) -
NievesGonzalez Aniel,
Clausen Chris,
Marcano Mariano,
Layton Harold E,
Layton Anita T,
Moore Leon C
Publication year - 2011
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.25.1_supplement.1041.21
Subject(s) - transcellular , paracellular transport , chemistry , sodium , biophysics , concentration gradient , chromatography , biochemistry , membrane , biology , organic chemistry , permeability (electromagnetism)
TAL cells are thought to transport Na + efficiently owing to passive paracellular Na + absorption, a phenomenon that is important in the outer medulla where O 2 availability is limited by low blood flow. We used a multiscale, cell‐based mathematical model of the TAL to estimate the efficiency of Na + transport along the TAL, and to examine what determines transport efficiency. The TAL model consists of epithelial cell models that represent all major solutes and transport pathways. The model equations are based on mass conservation and electroneutrality constraints. Empirical descriptions of cell volume regulation (CVR), pH control, and tubuloglomerular feedback (TGF) system are implemented in the model. Transport efficiency was calculated as the ratio of total net Na + transport to transcellular Na + transport. The results show that 1) CVR in individual cells influences the distribution of net NaCl transport along the TAL; 2) CVR responses in conjunction with TGF increases the overall efficiency of NaCl transport; 3) the transepithelial [Na + ] gradient is a major determinant of the transport efficiency; and 4) under conditions where the distribution of NaCl transport along the TAL is quasi‐uniform, the axial [Cl − ] gradient will be sufficiently steep to yield a TGF system dynamic gain consistent with experimental data. This research was supported by NIH grants DK‐89006, DK‐42091, SC1GM084744, and NSF grant DMS‐0701412.