Fig. 5.

CaSR signaling in TAL. Simplified model of CaSR by representative type I and type II agonists. The CaSR is located on basolateral cell membranes of TAL. Its activation inhibits cAMP formation mediated by Gαi and formation of lipid second messengers and prostanoids through phospholipase C (PLC) and cytoplasmic phospholipase A2 (cPLA2), respectively. Inhibition of Na⁺:K⁺:2Cl^– co-transport on apical cell membranes is indirect and mediated by blockade of ROMK by 20-HETE or PGE2. CaSR activation inhibits both PTH-stimulated calcium absorption and passive paracellular calcium absorption (not shown). Further details are provided in the text