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. Received: 4 July 1996 / Received after revision and accepted: 3 September 1996