VASOPRESSIN-STIMULATED CA2- EFFECTS ON CAMP AND CYTOSOLIC CA2+( REABSORPTION IN RABBIT CORTICAL COLLECTING SYSTEM )

The effect of arginine vasopressin (AVP) on transepithelial Ca2+ trans port in primary cultures of rabbit cortical collecting system cells wa s examined. Addition of AVP to the basolateral side of the monolayer d ose-dependently (EC(50)=0.7 nM) increased active Ca2+ reabsorption fro m a basal value of 85+/-2 nmol . h(-1). cm(-2) to a maximum value of 1 24+/-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 monophospha te (cAMP) content. Both effects of AVP were mimicked by the V-2 agonis t deamino-Cys,D-Arg(8)-vasopressin (dDAVP) and forskolin. Addition of either AVP or dDAVP to the basolateral side evoked a sustained increas e in cytosolic free Ca2+ concentration, which resulted from both Ca2entry 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 stimu lates transcellular Ca2+ transport in the cortical collecting system t hrough activation of basolateral V-2 receptors coupled to adenylyl cyc lase to increase the cellular cAMP content.