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Estimation of Collecting Duct Parameters for Maximum Urine Concentrating Capability in a Mathematical Model of the Rat Inner Medulla
Author(s) -
Marcano Mariano,
Layton Anita T.,
Layton Harold E.
Publication year - 2006
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.20.5.a1224-b
Subject(s) - urine , urea , chemistry , scaling , urine osmolality , chromatography , mathematics , biochemistry , geometry
A nonlinear optimization technique was used to estimate collecting duct (CD) parameter sets that maximize the urine‐to‐plasma osmolality ratio ( U/P ) in a mathematical model of the urine concentrating mechanism in the rat inner medulla. The parameters varied were: water flow and urea concentration of tubular fluid entering the CD at the outer‐inner medullary boundary; location and exponential increase rate of the urea permeability profile along the CD; and a scaling factor for the maximum active NaCl transepithelial transport rate of the CD. In the optimization algorithm, parameters were allowed to vary within ranges suggested by physiologic experiments. In addition, the optimization algorithm was constrained by a realistic lower limit for the urine flow. The optimization algorithm identified a set of parameters for maximum U/P that yielded urine osmolality and concentration values consistent with reported experimental values. This research was supported by NIH grants DK‐42091 and S06GM08102, and NSF grant DMS‐0340654.