Vasopressin-stimulated Ca2+ reabsorption in rabbit cortical collecting system: effects on cAMP and cytosolic Ca2+.

The effect of arginine vasopressin (AVP) on transepithelial Ca2+ transport in primary cultures of rabbit cortical collecting system cells was examined. Addition of AVP to the basolateral side of the monolayer dose-dependently (EC50 = 0.7 nM) increased active Ca2+ reabsorption from a basal value of 85 +/- 2 nmol.h-1.cm-2 to a maximum value of 124 +/- 3 nmol.h-1.cm-2. This was paralleled by a dose-dependent (EC50 = 1.1 nM) increase in cellular adenosine 3', 5'-cyclic monophosphate (cAMP) content. Both effects of AVP were mimicked by the V2 agonist deamino-Cys,D-Arg8-vasopressin (dDAVP) and forskolin. Addition of either AVP or dDAVP to the basolateral side evoked a sustained increase in cytosolic free Ca2+ concentration, which resulted from both Ca2+ entry and release from internal stores. Only the effect on Ca2+ entry was mimicked by forskolin, demonstrating that cAMP acts by activating a Ca2+ influx pathway. The present findings demonstrate that AVP stimulates transcellular Ca2+ transport in the cortical collecting system through activation of basolateral V2 receptors coupled to adenylyl cyclase to increase the cellular cAMP content.