PTH increases renal calcium reabsorption in which part of the nephron?

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Multiple Choice

PTH increases renal calcium reabsorption in which part of the nephron?

Explanation:
PTH increases calcium reabsorption at the distal tubule. In the late distal tubule, PTH binds its receptor and triggers cAMP/PKA signaling that boosts the activity and amount of apical calcium channels (TRPV5). More calcium then enters the tubular cells and is pumped out basolaterally via NCX and PMCA, so more calcium is reclaimed from the urine. The proximal tubule reabsorbs most calcium passively without direct PTH stimulation, and the loop of Henle and collecting duct contribute less to hormonally regulated calcium reabsorption. Thus, the distal tubule is the key site where PTH enhances renal calcium reabsorption.

PTH increases calcium reabsorption at the distal tubule. In the late distal tubule, PTH binds its receptor and triggers cAMP/PKA signaling that boosts the activity and amount of apical calcium channels (TRPV5). More calcium then enters the tubular cells and is pumped out basolaterally via NCX and PMCA, so more calcium is reclaimed from the urine. The proximal tubule reabsorbs most calcium passively without direct PTH stimulation, and the loop of Henle and collecting duct contribute less to hormonally regulated calcium reabsorption. Thus, the distal tubule is the key site where PTH enhances renal calcium reabsorption.

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