Functional and molecular evidence for p2x receptors in llc-pk1
cells.
Filipovic, Dragana M., Olugbenga A. Adebanjo, Mone Zaidi, and W. Brian
Reeves.
Division of Nephrology, University of Arkansas for Medical Sciences
and the John. L. McClellan Veterans Affairs Hospital, Little Rock, AR
72205, Geriatrics and Extended Care, Philadelphia VA Medical Center,
Philadelphia, PA, 19104
APStracts 5:0052F, 1998.
Extracellular ATP affects a wide variety of cells via purinergic
membrane receptors. One class of purinergic receptors, P2X, are ATP
-gated, calcium-permeable, cation-selective channels. We performed
whole cell patch clamp studies, intracellular calcium ([Ca2+]i)
measurements, and reverse transcriptase-polymerase chain reaction
(RT-PCR) to determine if P2X receptors are expressed in LLC-PK1
cells. First, in patch clamp studies, 100 (M ATP depolarized the cell
membrane and increased the whole cell conductance of LLC-PK1 cells.
This response was dose-dependent and inhibited by 100 (M suramin, a
P2 receptor antagonist. The ATP-induced conductance was cation
selective, but did not discriminate between Na+ and K+. ADP,
(,[beta]-methylene ATP and (,(-methylene ATP had no effect on the
whole cell conductance. Next, 10 (M ATP caused a rapid rise in
[Ca2+]i in LLC-PK1 cells. This effect of ATP was inhibited by the
absence of extracellular calcium and by suramin, but not by
pretreatment with pertussis toxin. ADP and (,(-methylene ATP had
little or no effect on [Ca2+]i. Finally, RT-PCR produced a 330 bp
fragment from LLC-PK1 cell RNA whose sequence was 80% identical to
the rat P2X1 receptor. We conclude that LLC-PK1 cells express
purinergic receptors of the P2X class which mediate depolarization
and calcium entry when activated.
Received 28 May 1997; accepted in final form 17 February 1998.
APS Manuscript Number F178-7.
Article publication pending Am. J. Physiol. (Renal Physiology).
ISSN 1080-4757 Copyright 1998 The American Physiological Society.
Published in APStracts on 9 March 1998