title: P2-purinoceptors utilize multiple signalling pathways in MDCK-D1 cells.
abstract: 1. Madin-Darby canine kidney (MDCK) cells are a widely used model system for the study of epithelial cells. We have utilized a clonal variant, MDCK-D1, to examine signalling by P2-purinoceptors. 2. Several lines of evidence that lead us to conclude that MDCK-D1 cells co-express P2a- and P2y-purinoceptors and that both subtypes are linked to the release of arachidonic acid and metabolites (AA) include: (a) relative potency of nucleotide analogues in promoting AA release; (b) blockade by the antagonist suramin of response to the P2Y-selective agonist, 2-methylthio ATP (2-MT-ATP), but not to the P2a-selective agonist, UTP; and (c) additivity of response to 2-MT-ATP and UTP. AA release is a consequence of activation of phospholipase A2 (PLA2), most likely the 85 kDa cytosolic PLA2. 3. Treatment of MDCK-D1 cells with ATP, but not UTP, increases inositol 1,4,5-trisphosphate formation while both UTP and ATP increase phosphatidylcholine hydrolysis, ATP, UTP, and 2-MT-ATP can also stimulate phospholipase D activity. 4. Purine nucleotides increase cellular cAMP levels in MDCK-D1 cells in a manner that depends, at least in part, on activation of cyclooxygenase, since cAMP generation stimulated by ATP or UTP is inhibited by treatment of cells with indomethacin. Because cyclooxygenase-derived PGE2 can bind to prostaglandin receptors and stimulate synthesis of cAMP, nucleotides may raise cAMP in an autocrine or paracrine fashion. 5. Taken together, these results indicate that MDCK-D1 cells co-express P2a and P2y-purinoceptors and that these receptors utilize several mechanisms to regulate cell function, including activation of multiple phospholipases and autocrine/paracrine action of products.
authors.affiliation: Dept of Pharmacology, University of California, San Diego, La Jolla 92093, USA.
authors.forename: P A
authors.initials: PA
authors.lastname: Insel
authors.forename: B L
authors.initials: BL
authors.lastname: Firestein
authors.forename: M
authors.initials: M
authors.lastname: Xing
authors.forename: S R
authors.initials: SR
authors.lastname: Post
authors.forename: J P
authors.initials: JP
authors.lastname: Jacobson
authors.forename: M A
authors.initials: MA
authors.lastname: Balboa
authors.forename: R J
authors.initials: RJ
authors.lastname: Hughes
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D016718:Arachidonic Acid / Q000378:metabolism; D002478:Cells, Cultured; D000242:Cyclic AMP / Q000378:metabolism; D004285:Dogs; D066298:In Vitro Techniques; D015544:Inositol 1,4,5-Trisphosphate / Q000096:biosynthesis; D007668:Kidney / Q000166:cytology / Q000378:metabolism*; D010713:Phosphatidylcholines / Q000378:metabolism; D018048:Receptors, Purinergic P2 / Q000378:metabolism*; D015398:Signal Transduction; D014544:Uridine Triphosphate / Q000494:pharmacology
chemical_list: D010713:Phosphatidylcholines; D018048:Receptors, Purinergic P2; D016718:Arachidonic Acid; D015544:Inositol 1,4,5-Trisphosphate; D000255:Adenosine Triphosphate; D000242:Cyclic AMP; D014544:Uridine Triphosphate