Nucleotides regulate NaCl transport in mIMCD-K2 cells via P2X and P2Y purinergic receptors

MCCoy, David E., Amanda L. Taylor, Brian A. Kudlow, Katherine Karlson, Margaret J. Slattery, Lisa M. Schwiebert, Erik M. Schwiebert, and Bruce A. Stanton. Nucleotides regulate NaCl transport in mIMCD-K2 cells via P2X and P2Y purinergic receptors. Am. J. Physiol. 277 (Renal Physiol. 46): F552-F559, 1999.--Extracellular nucleotides regulate NaCl transport in some epithelia. However, the effects of nucleotide agonists on NaCl transport in the renal inner medullary collecting duct (IMCD) are not known. The objective of this study was to determine whether ATP and related nucleotides regulate NaCl transport across mouse IMCD cell line (mIMCD-K2) epithelial monolayers and, if so, via what purinergic receptor subtypes. ATP and UTP inhibited [Na.sup.+] absorption [measured via [Na.sup.+] short-circuit current ([MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII])] and stimulated [Cl.sup.-] secretion [measured via [Cl.sup.-] short-circuit current ([MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII])]. Using selective P2 agonists, we report that P2X and P2Y purinoceptors regulate [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] and [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII]. By RT-PCR, two P2X receptor channels ([P2X.sub.3], [P2X.sub.4]) and two P2Y G protein-coupled receptors ([P2Y.sub.1], [P2Y.sub.2]) were identified. Functional localization of P2 purinoceptors suggest that [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] is stimulated by apical membrane-resident P2Y purinoceptors and P2X receptor channels, whereas [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] is inhibited by apical membrane-resident P2Y purinoceptors and P2X receptor channels. Together, we conclude that nucleotide agonists inhibit [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] across mIMCD-K2 monolayers through interactions with P2X and P2Y purinoceptors expressed on the apical plasma membrane, whereas extracellular nucleotides stimulate [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] through interactions with P2X and P2Y purinoceptors expressed on the apical plasma membrane. inner medullary collecting duct; short-circuit current; kidney