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 (EC(50)=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 (EC(50)=1.1 nM) increase in cellular adenosine 3',5'-cyclic monophosphate (cAMP) content. Both effects of AVP were mimicked by the V-2 agonist deamino-Cys,D-Arg(8)-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 V-2 receptors coupled to adenylyl cyclase to increase the cellular cAMP content.