Abstract
Our knowledge of the kidney in development, particularly its structure, is very limited. We used a mathematical model in conjunction with optimization problems to study the urine production capability of a medullary structure consisting of two populations of Henleˈs loops at different levels of development. In the model, the descending limb has heterogeneous transport properties along the medulla and the ascending limb only has a thick segment. The model parameters consist of membrane transport rates and boundary values for water flows and solute concentrations, and their baseline values were obtained from reported means in physiological experiments or they were estimated using physiological assumptions. By maximizing the solute free‐water absorption (FWA) and using parameter ranges from physiological experiments of neonatal rats in antidiuresis, we obtained results that yield a urine osmolality of 479 mOsmol/KgH2O and a urine flow of 0.126 nl/min per nephron. By minimizing the FWA and using parameter ranges from experiments of neonatal rats in diuresis, the results produced a urine osmolality of 75 mOsmol/KgH2O and a urine flow of 0.962 nl/min per nephron. These results are in agreement with the statement that the neonatal mammalian kidney can dilute urine as efficiently as the mature kidney, but its concentrating capability is limited.Research supported by NIH‐NIGMS grant SC1GM084744.
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