Inhibition of na+ and ca2+ reabsorption by p2u-purinoceptors
requires protein kinase c but not ca2+ signaling.
Koster, Henk P. G., Anita Hartog, Carel H. Van Os, and
Ren[circumflex]a J. M. Bindels.
Department of Cell Physiology, University of Nijmegen, P.O. Box
9101, 6500 HB Nijmegen, The Netherlands
APStracts 2:0123F, 1995.
Rabbit connecting tubule and cortical collecting duct cells were
isolated by immunodissection and cultured to confluency on permeable
filters and on glass coverslips. Extracellular ATP dose-dependently
reduced transcellular Na+ and Ca2+ transport (IC50= 0.5 0.2 and 3.2
0.5 M), with a maximal inhibition of 57 5 and 43 4 %, respectively.
Purinergic receptor agonists inhibited transport with the following
rank order of potency: UTP=ATP>ADP, suggesting involvement of
P2u-purinoceptors. ATP also caused a dose-dependent (EC50= 1.5 0.2 M)
transient increase in intracellular Ca2+ concentration ([Ca2+]i)
which decreased to a sustained elevated level. In the absence of
extracellular Ca2+, a similar Ca2+ transient occurred, but the
sustained response was abolished. Preloading the cells with the Ca2+
chelator BAPTA completely prevented the ATP-induced Ca2+ transients,
but not the ATP-induced inhibition of Na+ and Ca2+ absorption.
Activation of protein kinase C (PKC) by the cell permeable 1,2
-dioctanoyl-sn-glycerol mimicked ATP-induced inhibition of Na+ and
Ca2+ absorption. The inhibitory effects of ATP were no longer
observed after culturing cells in the presence of phorbol ester (TPA)
for 5 days which resulted in down-regulation of cellular PKC
activity.
Received 31 January 1995; accepted in final form 22 June 1995.
APS Manuscript Number F28-5.
Article publication pending Am. J. Physiol. (Renal Fluid Electrolyte
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 30 July 1995.