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 (ECM ) = 0.7 nM) increased active Ca2+ reab sorption from a basal value of 85 ± 2 nm oM r'-cnr2 to a maximum value of 124 ± 3 nniol-lr^cnr2. This was par alleled by a dose-dependent (ECi0 =1.1 nM ) increase in cellular adenosine ¿'^'-cyclic monophosphate (cAMP) content. Both effects of AVP were mimicked by the V 2 agonist deamino-Cys,D-Arg8-vasopressin (dDAVP) and forskolin. Addition of either AVP or dDAVP to the baso lateral 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 pres ent findings demonstrate that AVP stimulates transeellular Ca2'1 * transport in the cortical collecting system through activation of basolateral V 2 receptors coupled to adenylyl cyclase to increase the cellular cAM P content.