Nephron Sites of Adaptation to Changes in Dietary Phosphate
Studies of the renal adaptation to changes in the dietary intake of phosphate have provided important insights into the mechanisms of regulation of phosphate transport by the renal tubule, Troehler, Bonjour and Fleisch (1) and Steele and DeLuca (2) showed that phosphate deprivation results in marked increases in phosphate transport which were independent of plasma phosphate and parathyroid hormone. Further, rats fed a low phosphate diet provide a model of resistance to the Phosphaturic response to PTH (3). Whereas the expected increase in cAMP generation and hypocalciuria occur, there is no increase in phosphate excretion. Studies utilizing several different approaches support the concept that adaptive changes in phosphate transport occur in the proximal tubule. In vivo microperfusion, isolated tubule and isolated renal brush border vesicle studies of proximal tubules all illustrate enhanced phosphate transport in animals fed a low phosphate diet (4, 5, 6, 7). Micropuncture studies in dogs also show enhanced phosphate reabsorption in the proximal tubule in phosphate deprivation (8, 9). Accordingly, adaptation of proximal tubule phosphate transport is very likely. However, the contribution of this altered transport to the urinary excretion of phosphate remains controversial.
KeywordsProximal Tubule Phosphate Transport Phosphate Reabsorption Phosphate Diet Micropuncture Study
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