Apical P2XR contribute to [Ca2+]i signaling and Isc in mouse renal MCD.

Abstract We examined P2X receptor expression and distribution in the mouse collecting duct (CD) and their functional role in Ca 2+ signaling. Both P2X 1 and P2X 4 were detected by RT-PCR and Western blot. Immunohistochemistry demonstrated apical P2X 1 and P2X 4 immunoreactivity in principal cells in the outer medullary CD (OMCD) and inner medullary CD (IMCD). Luminal ATP induced an increase in Ca 2+ signaling in native medullary CD (MCD) as measured by fluorescence imaging. ATP also induced an increase in Ca 2+ signaling in MCD cells grown in primary culture but not in the presence of P2XR antagonist PPNDS. Short circuit current ( I sc ) measurement with mouse IMCD cells showed that P2XR agonist BzATP induced a larger I sc than did P2YR agonist UTP in the apical membrane. Our data reveal for the first time that P2X 1 and P2X 4 are cell-specific with prominent immunoreactivity in the apical area of MCD cells. The finding that P2XR blockade inhibits ATP-induced Ca 2+ signaling suggests that activation of P2XR is a key step in Ca 2+ -dependent purinergic signaling. The result that activation of P2XR produces large I sc indicates the necessity of P2XR in renal CD ion transport.