Involvement of the V2 receptor in vasopressin-stimulated translocation of placental leucine aminopeptidase/oxytocinase in renal cells.

The placental leucine aminopeptidase (P-LAP)/oxytocinase is a membrane-bound enzyme thought to play an important role during pregnancy. In this study, we identified the presence of P-LAP protein in the renal distal tubules and collecting ducts. In rat NRK52E cells derived from renal tubules, P-LAP was localized mainly in the intracellular compartment. Upon the treatment of cells with 8-arginine-vasopressin (AVP), a significant increase in the surface level of P-LAP was observed. deamino-Cys1, d-Arg8]-vasopressin (DDAVP), a specific V2 receptor agonist, increased the surface level of P-LAP, while adamantaneacetyl1, O-Et-d-Tyr2, Val4, aminobutyryl6, Arg8,9]-vasopressin (AEAVP), a potent V2 receptor antagonist, blocked the AVP-stimulated enhancement. Moreover, reagents known to enhance the intracellular level of cAMP have also been shown to increase the surface level of P-LAP. When we examined the colocalization of P-LAP with the cell surface water channel aquaporin-2 (AQP-2) that is regulated by AVP, the P-LAP-containing vesicles had a relatively higher density than the AQP-2-containing vesicles, suggesting that P-LAP and AQP-2 are differently distributed in NRK52E cells. These results suggest that AVP induces the translocation of P-LAP via V2 receptor and P-LAP plays a role in the regulation of excessive AVP level in the renal collecting duct, acting as a negative feedback mechanism for the AVP action of regulating water reabsorption.