Renal Pi Transport in Young Growing and Adult Rats: Comparative Studies in Brush Border Membrane Vesicles (BBMV) and in Whole Kidney
The question where and how the renal transport of inorganic phosphate (Pi) is regulated has been the subject of numerous investigations over the last few years. In this regard, the discovery of a sodium-dependent Pi transport system in the brush border membranes of the renal cortex (1) has been of particular interest. It gave rise to the question of whether the Pi transfer rate determined by this system across the luminal membrane of the proximal tubule would be the only limited and regulated step of the overall net tubular Pi reab-sorption. Therefore we have been particularly interested in studying the relationship between alterations in the overall tubular Pi reabsorptive capacity and changes in the Pi transport at the level of brush border membrane vesicles (BBMV) of the renal cortex of rats. In this investigation the alterations in the renal handling of Pi were provoked by variation in dietary Pi, removal of the parathyroid gland, chronic administration of either 1,25-dihydroxyvitamin D to thyroparathyroidectomized animals or the diphosphonate ethane-1-hydroxy-1,1-diphosphonate (2,3).
KeywordsProximal Tubule Renal Cortex Brush Border Membrane Vesicle Luminal Membrane Renal Handling
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