Clinical journal of the American Society of Nephrology : CJASN
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Clin J Am Soc Nephrol · Oct 2014
Urine-concentrating mechanism in the inner medulla: function of the thin limbs of the loops of Henle.
The ability of mammals to produce urine hyperosmotic to plasma requires the generation of a gradient of increasing osmolality along the medulla from the corticomedullary junction to the papilla tip. Countercurrent multiplication apparently establishes this gradient in the outer medulla, where there is substantial transepithelial reabsorption of NaCl from the water-impermeable thick ascending limbs of the loops of Henle. However, this process does not establish the much steeper osmotic gradient in the inner medulla, where there are no thick ascending limbs of the loops of Henle and the water-impermeable ascending thin limbs lack active transepithelial transport of NaCl or any other solute. ⋯ A possible role for the three-dimensional interactions between these inner medullary tubules and vessels in the concentrating process is suggested by creation of physiologic models that depict the three-dimensional relationships of tubules and vessels and their solute and water permeabilities in rat kidneys and by creation of mathematical models based on biologic phenomena. The current mathematical model, which incorporates experimentally determined or estimated solute and water flows through clearly defined tubular and interstitial compartments, predicts a urine osmolality in good agreement with that observed in moderately antidiuretic rats. The current model provides substantially better predictions than previous models; however, the current model still fails to predict urine osmolalities of maximally concentrating rats.
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The National Institute of Diabetes and Digestive and Kidney Diseases-supported Kidney Research National Dialogue asked the scientific community to formulate and prioritize research objectives that would enhance understanding of kidney function and disease and improve clinical outcomes. An engaged and growing group of investigators working in type 2 translation (from clinical evidence to implementation in the community) identified barriers to improving patient care in CKD and suggested research priorities to test translational strategies that have been effective for other chronic diseases.