Characterization of a functional V1Bvasopressin receptor in the male rat kidney, evidence for crosstalk between V1Band V2 receptor signaling pathways

Although vasopressin V1Breceptor (V1B-R) mRNA was detected in the kidney, the precise renal localization, pharmacological and physiological properties of this receptor remain unknown. Using the selective V1Bagonist d[Leu4, Lys8]VP, either fluorescent or radioactive, we showed that V1B-R is mainly present in principal cells of the inner medullary collecting duct (IMCD) in the male rat kidney. Protein and mRNA expression of V1B-R were very low compared to V2 receptor (V2-R). On microdissected IMCD, d[Leu4, Lys8]VP had no effect on cAMP production but induced a dose-dependent and saturable [Ca2+]iincrease mobilization with an EC50in the nanomolar range. This effect involved both intracellular calcium mobilization and extracellular calciuminflux. The selective V1Bantagonist SSR149415 strongly reduced the ability of vasopressin to increase [Ca2+]ibut also cAMP suggesting a cooperation between V1B-R and V2-R in IMCD cells expressing both receptors. This cooperation arises from a crosstalk between second messenger cascade involving protein kinase C rather than receptor heterodimerization as supported by potentiation of the AVP-stimulated cAMP production in HEK293 cells co-expressing the two receptor isoforms and negative results obtained by bioluminescence resonance energy transfer experiments. In vivo, only acute administration of high doses of V1Bagonist triggered significant diuretic effects by contrast with injection of selective V2agonist. This study brings new data on the localization and signaling pathways of V1B-R in the kidney, highlights a crosstalk between V1B-R and V2-R in IMCD and suggests that V1B-R may counterbalance in some pathophysiological conditions the antidiuretic effect triggered by V2-R activation.