An active, transcellular process
70% in proximal tubule
20% in thick ascending limb of Loop of Henle
10% in distal convoluted tubule

activates Ca2+ entry channels on the apical membrane of distal tubule
activates Ca/ATPase pump on the basolateral membrane
= Ca influx to tubule cells + Ca out to interstitial space

activates Ca2+/ATPase pump on basolateral membrane 🏠 distal collecting tubule
= ↑ Ca reabsorption

released from parafollicular cells of parathyroid
net effect: ↓ plasma Ca
= inhibits Ca2+ and PO4 resorption by renal tubular cells (so it gets peed out)

#renal #endocrine