Heterogeneity of p2u- and p2y- purinergic receptor regulation of
phospholipases in madin-darby canine kidney cells.
Firestein, Bonnie L., Mingzhao Xing, Richard J. Hughes, Carlos U.
Corvera, and Paul A. Insel.
Department of Pharmacology and Program in Neurosciences, School of
Medicine, UCSD, La Jolla, CA 92093-0636
APStracts 3:0092F, 1996.
We have characterized the signaling pathways of purinergic receptors
present on the renal epithelial cell line, Madin-Darby canine kidney
(MDCK, D-1 subclone). Several lines of evidence are consistent with
the conclusion that co-existing P2U and P2Y receptors release
arachidonic acid and metabolites (AA) from MDCK-D1 cells: 1) Relative
potencies of nucleotide analogs; 2) Blockade of P2Y agonist-, but not
P2U, agonist-mediated release by suramin; and 3) Additivity by 2MT
-ATP and UTP. Differences exist between the signaling pathways of the
two receptors: pertussis toxin treatment partially inhibits P2U-, but
not P2Y-, mediated AA release and P2Y- (but not P2U) receptors appear
to stimulate inositol 1,4,5-trisphosphate (IP3) production. P2U
receptor occupancy results in both homologous and heterologous
desensitization; P2Y-receptor occupancy elicits only homologous
desensitization. Both receptors stimulate phosphatidylcholine
hydrolysis via phospholipase C (PLC) activation. However, AA release
appears to result from phospholipid deacylation by phospholipase A2
(PLA2) activation rather than from alternate pathways that may
include PLC activation. These results demonstrate for the first time
that two subtypes of P2-purinergic receptors, P2U and P2Y receptors,
co-exist on a single renal epithelium cell type and that these two
receptor subtypes can promote AA release, probably via activation of
PLA2.
Received 5 September 1995; accepted in final form 8 May 1996.
APS Manuscript Number F292-5.
Article publication pending Am. J. Physiol. (Renal Fluid Electrolyte
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 28 May 96