Vasopressin stimulates long-term net chloride secretion in cortical collecting duct cells

The classical short-term effect (within minutes) of arginine vasopressin (A VP) consists in increasing sodium, chloride and water transport in kidney c ells, More recently, long-term actions (several hours) of the hormone have been evidenced on water and sodium fluxes, due to transcriptional enhanceme nt in the expression of their transporters. The present study demonstrates that AVP is also responsible for a long-term increase in net chloride secre tion. In the RCCD1 rat cortical collecting duct cell line, 10(-8) M AVP ind uced, after several hours, an increase in net Cl-36(-) secretion. This dela yed effect of AVP was inhibited by basal addition of 10(-4) M bumetanide an d apical addition of 10(-4) RI glibenclamide, suggesting chloride entry at the basal membrane through a Na+/K+/2Cl(-) and apical secretion through a c hloride conductance. An original acute cell permeabilization method was dev eloped to allow for entry of antibodies directed against the regulatory reg ion (R) of the cystic fibrosis transmembrane regulator (CFTR) into the cell s, This procedure led to a complete and specific blocking of the longterm n et chloride secretion induced by AVP, Finally, it was observed that CFTR tr anscripts steady-state level was significantly increased by AVP treatment. Besides the well-documented short-term effect of AVP on chloride transport, these results provide evidence that in RCCD1 cells, AVP induces a delayed increase in transepithelial net chloride secretion that is mediated by a Na +/K+/2Cl(-) co-transporter and CFTR, (C) 1999 Federation of European Bioche mical Societies.