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首页> 外文期刊>American Journal of Physiology >A region-based mathematical model of the urine concentrating mechanism in the rat outer medulla. II. Parameter sensitivity and tubular inhomogeneity.
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A region-based mathematical model of the urine concentrating mechanism in the rat outer medulla. II. Parameter sensitivity and tubular inhomogeneity.

机译：大鼠外延髓中尿液浓缩机制的基于区域的数学模型。二。参数敏感性和管状不均匀性。

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摘要

In a companion study (Layton AT and Layton HE. Am J Physiol Renal Physiol 289: F1346-F1366, 2005), a region-based mathematical model was formulated for the urine concentrating mechanism (UCM) in the outer medulla (OM) of the rat kidney. In the present study, we quantified the sensitivity of that model to several structural assumptions, including the degree of regionalization and the degree of inclusion of short descending limbs (SDLs) in the vascular bundles of the inner stripe (IS). Also, we quantified model sensitivity to several parameters that have not been well characterized in the experimental literature, including boundary conditions, short vasa recta distribution, and ascending vasa recta (AVR) solute permeabilities. These studies indicate that regionalization elevates the osmolality of the fluid delivered into the inner medulla via the collecting ducts; that model predictions are not significantly sensitive to boundary conditions; and that short vasa recta distribution and AVR permeabilities significantly impact concentrating capability. Moreover, we investigated, in the context of the UCM, the functional significance of several aspects of tubular segmentation and heterogeneity: SDL segments in the IS that are likely to be impermeable to water but highly permeable to urea; a prebend segment of SDLs that may be functionally like thick ascending limb (TAL); differing IS and outer stripe Na(+) active transport rates in TAL; and potential active urea secretion into the proximal straight tubules. Model calculations predict that these aspects of tubular of segmentation and heterogeneity generally enhance solute cycling or promote effective UCM function.
机译：在一项伴随研究中（Layton AT和Layton HE。Am J Physiol Renal Physiol 289：F1346-F1366，2005），针对尿液外延髓（OM）的尿液浓缩机制（UCM）制定了基于区域的数学模型。大鼠肾脏。在本研究中，我们量化了该模型对几个结构假设的敏感性，包括区域化程度和内条纹（IS）血管束中短下降肢（SDL）的包涵程度。此外，我们还对模型参数的敏感性进行了量化，这些参数在实验文献中尚未得到很好的描述，包括边界条件，短瓦萨直肠分布和升瓦萨直肠（AVR）溶质渗透率。这些研究表明，区域化会提高通过收集导管输送到髓质内的渗透压;模型的预测对边界条件不是很敏感;短的vasa直肠分布和AVR渗透性会显着影响浓缩能力。此外，我们在UCM的背景下研究了管状分段和异质性几个方面的功能意义：IS中的SDL片段可能不透水，但对尿素的透性高; SDL的弯曲前段，其功能可能类似于粗大上升肢（TAL）; TAL中不同的IS和外部条带Na（+）主动传输率;和潜在的活性尿素分泌到近端直小管中。模型计算预测，分段和异质性的这些方面通常会增强溶质循环或促进有效的UCM功能。

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