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0007-4888/00/0010-961$25.00 ©2000 Plenum Publishing Corporation
PHARMACOLOGY AND TOXICOLOGY
Effect of Temperature on Guinea Pig Urinary Bladder
Contraction Mediated via P2X-Receptors
A. U. Ziganshin, A. V. Rychkov, and L. E. Ziganshina
Translated from Byulleten Eksperimentalnoi Biologii i Meditsiny , Vol. 130, No. 10, pp. 407-410, October, 2000
Original article submitted February 16, 2000
In vitro experiments showed that P2X-receptor agonist α,β-methylene-ATP and electrical
field stimulation in the presence of muscarinic and α-adrenoreceptors blockers induced con-
tractile responses of isolated guinea pig bladder, which were more pronounced at 30
o
C than
at 37
o
C or 42
o
C. P2X-receptor antagonist pyridoxal-6-phosphate-2,4-disulfonic acid, pro-
duced a more potent inhibitory effect on contractions induced by electrical field stimulation
at 30
o
C in comparison with that at 37
o
C or 42
o
C, while the contractions induced by α,β-me-
thylene-ATP were similarly suppressed at all examined temperatures.
Key Words: P2X-receptors; bladder; temperature dependence
Department of Pharmacology, Kazan State Medical University
ATP receptors (P2-receptors) were revealed in various
tissues, the bladder of guinea pig included [1]. Acti-
vation of these receptors with α,β-methylene-ATP, an
agonist of P2X-receptors, or electric field induces pha-
sic contractions, which are inhibited with P2X-recep-
tor antagonists suramin and pyridoxal-6-phosphate-
2,4-disulfonic acid (PPADS) [6,12,13]. Most experi-
ments with P2-receptors were carried out under standard
physiological conditions; however, there is evidence
that the responses mediated by P2-receptors depend on
pH [7,10]. Our aim was to study the effect of tempe-
rature on the contractile responses mediated by P2X-
receptors.
MATERIALS AND METHODS
Guinea pigs weighing 350-550 g were euthanized and
dehematized. The bladder was isolated, 2×10-mm
smooth muscle preparations were prepared and placed
in 10-ml thermostabilized vials to measure isomeric
contraction. The tissue was rested under a load of 1 g
for about 1 h to adapt to the medium. Electrical field
stimulation (EFS) was performed with two platinum
rings with a diameter of 2.5 mm, through which the
muscle strip was threaded. The modified Krebs so-
lution contained (in mM): 133 NaCl, 4.7 KCl, 16.3
NaHCO
3
, 0.6 MgCl
2
, 1.35 NaHPO
4
, 2.5 CaCl
2
, 7.8
C
2
H
12
O
6
, oxygenated with 95% O
2
and 5% CO
2
(pH
7.3-7.4). In EFS experiments, atropine (3×10
7
M)
and phentolamine (10
6
M) were added. The contrac-
tions were measured with an FSG-01 transducer (Lin-
ton) coupled with a Biopack digitizer and imputed to
PC. EFS was performed with a Grass S9 stimulator.
The duration, amplitude, and frequency of pulses were
0.5 msec, 100 V, and 1-64 Hz, respectively. α,β-Me-
thylene-ATP (10
8
-3×10
5
M) was added to vials, and
after attaining the maximum contraction the prepara-
tion was rapidly washed several times in fresh Krebs
solution to prevent desensitization of P2X-receptors.
All contractile responses were calculated as the per-
centage of maximum response to KCl (240 mM),
which was introduced into the solution at the end of
the experiment.
The temperature was regulated with a Techne
TE-8A pump by changing the temperature of circula-
ting fluid. In all experiments, the initial stages and ad-
aptation were carried out at 37±1
o
C. Two successive
contractions induced by α,β-methylene-ATP (3×10
6
Bulletin of Experimental Biology and Medicine, Vol. 130, No. 10, October, 2000