All of the following electrolytes are absorbed in distal convoluted tubule (DCT), EXCEPT:
Correct Answer: K+
Description: Only about 10% of the filtered NaCl is reabsorbed in the distal convoluted tubule (DCT). Like the TAL of Henle's loop, this segment is relatively impermeable to water, and NaCl reabsorption fuher dilutes the tubular fluid. The mechanism of NaCl transpo in the DCT is an electrically neutral thiazide-sensitive Na+ and Cl- cotranspoer. Because K+ does not recycle across the apical membrane of the DCT as it does in the TAL, there is no lumen-positive potential in this segment. Ca2+ is actively reabsorbed by the DCT epithelial cell an apical Ca2+ channel and basolateral Na+/Ca2+ exchanger. This process is regulated by parathyroid hormone. Ref: Eaton D.C., Pooler J.P. (2009). Chapter 6. Basic Renal Processes for Sodium, Chloride, and Water. In D.C. Eaton, J.P. Pooler (Eds), Vander's Renal Physiology, 7e.
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