Phosphoinositidase c-sensitive to purine and pyrimidine nucleotides
in ampulla from frog semicircular canal.
Butlen, Daniel, Christian Bernard, Abderrahim Ammar, and Evelyne
Ferrary.
Institut National de la Sant[acute]e et de la Recherche
M[acute]edicale U. 426, D[acute]epartement de Physiologie,
Facult[acute]e de M[acute]edecine Xavier Bichat, 16, rue Henri
Huchard, 75870 Paris Cedex 18, France, Laboratoire de
Neurophysiologie Sensorielle, Universit[acute]e de Rouen, 76821 Mont
-Saint-Aignan Cedex, France
APStracts 3:0305R, 1996.
A microassay was developed to screen the abilities of ATP analogues to
stimulate phosphoinositidase C in single ventral regions (including
dark cells and sensory cells) of ampullas microdissected from
posterior vertical semicircular canals of Rana ridibunda and labeled
with myo-[3H]-inositol. ATP induced a dose-dependent and saturable
increase of total [3H]-inositol phosphates production accompanied by
an equivalent decrease in [3H]-phosphoinositide pool. The rank order
of analogues revealing agonistic potencies for phosphoinositidase C
activation was as follows : UTP >/= ATP-[gamma]-S >/= ADP-[beta]-S
>/= ATP >/= ADP = ITP >/= GTP >/= 2-MeS-ATP = XTP >/= dTTP >/= CTP =
([alpha], [beta])-Me-ATP > 5'-AMP, whereas cyclic AMP and
adenosine were almost devoid of activity. For antagonists, DIDS was
far more active than suramin for competitive inhibition of ATP
-induced enzyme stimulation, whereas reactive blue 2 acted as a
noncompetitive inhibitor. Results indicate that the putative P2
receptors triggering phosphoinositidase C activation in ventral
ampullary epithelium from frog semicircular canal exhibit mainly the
functional properties of P2Y and P2U receptors.
Received 12 April 1996; accepted in final form 18 July 1996.
APS Manuscript Number R211-6.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 29 August 1996