The mechanism of intracellular ca2+ increase by extracellular atp
in isolated rabbit renal proximal tubules.
Yamada, Hideomi, George Seki, Shigeo Taniguchi, Shu Uwatoko, Keiji
Suzuki, and Kiyoshi Kurokawa.
First Dept. of Internal Medicine, Tokyo University School of
Medicine, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113, Japan, and * Health
Service Center, Tokyo University of Agriculture and Technology, 3-8-1
Harumicho, Fuchu city, Tokyo 183, Japan
APStracts 2:0396C, 1995.
The effects of extracellular ATP on cytosolic calcium concentrations
([Ca2+]i) and cell membrane potentials (Vb) of rabbit renal proximal
tubules were investigated using fura-2 and microelectrodes. ATP
transiently increased [Ca2+]i without an apparent sustained phase,
and the maximum effect was obtained at 10 M. ADP, adenosine 5'-O-3
-thiotriphoshate, and 2-methylthioadenosine 5'-triphosphate were
equally effective as ATP, while UTP, adenosine, and a, b -
methyleneadenosine 5'-triphosphate were far less effective. The
[Ca2+]i responses to ATP were strongly inhibited by reactive blue 2,
a P2- purinergic receptor antagonist. The removal of extracellular
Ca2+ as well as the addition of thapsigargin also markedly attenuated
the responses to ATP. In addition ATP had virtually no effect on Vb
except for the occasional small depolarization by 300 M ATP. These
results indicate that extracellular ATP increases [Ca2+]i through a
P2- purinergic receptor, and that this effect of ATP is dependent on
both extracellular and intracellular Ca2+.
Received 24 May 1995; accepted in final form 24 October 1995.
APS Manuscript Number C300-5.
Article publication pending Am. J. Physiol. (Cell Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 30 November 95