Permeability of medullary nephron segments to urea and water: Effect of vasopressin

Rocha, Antonino S.; Kokko, Juha P.

doi:10.1038/ki.1974.123

Cited by 107 publications

(41 citation statements)

References 21 publications

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“…Recently, Roch-Ramel et al (1978) and Gunther and Rabinowitz (1980) have reported non-equilibrium of urea between urine and papillary tissue water of rabbits. Because of these experimental findings they suggested a low urea permeability of the collecting duct epithelium in the inner medulla, a conclusion which is in conflict with measurements of Rocha and Kokko (1974). The present model shows that the observations by Roch-Ramel et al (1978) and Gunther and Rabinowitz (1980) do not contradict the high urea permeability reported by Rocha and Kokko (1974).…”

Section: Dct/cnt and Collecting Ductcontrasting

confidence: 57%

“…Rather, this gradual transition seems reasonable as some parameters differ substantially between OMCD and IMCD. This transition zone does not contradict the measurements of Rocha and Kokko (1974) as these data were obtained in the papillary CD. However, between the tALH and the TALH a discontinuous change of the parameters was incorporated in the model.…”

Section: Model Parameters For the Base Casementioning

confidence: 40%

“…Their very low value (0.097) is backed by the general assumption of almost impermeability of the OMCD for urea . Nevertheless, a simulation run using the higher OMCD urea permeability (0.34) of Rocha and Kokko (1974) will also be presented.…”

Section: Model Parameters For the Base Casementioning

confidence: 99%

“…2) The mathematical model study of the collecting duct system demonstrates that the measured non-equilibrium of urea between urine and papillary tissue water (Roch-Ramel et al, 1978;Gunther and Rabinowitz, 1980) does not contradict a relatively high urea permeability of the papillary collecting duct (Rocha and Kokko, 1974).…”

Section: Introductionmentioning

confidence: 99%

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Renal countercurrent system: Role of collecting duct convergence and pelvic urea predicted from a mathematical model

1983

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Abstract.A differential equation model of the renal countercurrent system has been developed and physiological data from nephron segments were incorporated together with recently suggested urea recycling from renal pelvis to inner medulla and, particularly, an exponential reduction in the number of collecting tubules towards the renal papilla. The role of these features for the countercurrent concentrating mechanism has been studied by simulation runs. The computations, using the multiple shooting method, provide predictions about concentration profiles for salt and urea in tubes (nephron segments) and in the central core along the entire medullary countercurrent system. The results indicate that this model, without active salt or urea transport in the inner medulla, yields concentration gradients along the medullary axis compatible with those measured in the tissue.

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Section: Dct/cnt and Collecting Ductcontrasting

confidence: 57%

Section: Model Parameters For the Base Casementioning

confidence: 40%

Section: Model Parameters For the Base Casementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Renal countercurrent system: Role of collecting duct convergence and pelvic urea predicted from a mathematical model

1983

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“…In the outermost part (4.5 < s < 6.5), the urea permeability (P 42 , 10" 5 cm/s) is allowed to vary between the bounds 1.1 [56] and 2.4 [61]. In the innermost part (8.25 < s < 10.5), the corresponding bounds are 2.4 [61] and 14.9 [56]. The interval 6.5 < s < 8.25 is modeled as a linear transition zone for P 42 .…”

Section: Simulationsand Resultsmentioning

confidence: 99%

The kidney model as an inverse problem

Breinbauer¹,

Lory

1991

Applied Mathematics and Computation

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The mammalian kidney is modeled by a multipoint boundary-value problem for a System of nonlinear ordinary differential equations. A corresponding inverse problem is presented, which allows the rigorous judgement of the potential of the given modeling technique. For its numerical Solution a discretization is proposed, which is tailor-made for kidney models. It leads to a nonlinear-programming problem with nonlinear equality and inequality constraints. The suggested methods are applied to current research problems in renal physiology.

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The Use and Abuse of Diuretics

Francisco¹

1982

Arch Intern Med

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Permeability of medullary nephron segments to urea and water: Effect of vasopressin

Cited by 107 publications

References 21 publications

Renal countercurrent system: Role of collecting duct convergence and pelvic urea predicted from a mathematical model

Renal countercurrent system: Role of collecting duct convergence and pelvic urea predicted from a mathematical model

The kidney model as an inverse problem

The Use and Abuse of Diuretics

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