Extracellular ca2+ decreases chloride reabsorption in rat ctal by
inhibiting camp pathway.
Ferreira, Marie C_leste De Jesus, and Claire Bailly.
URA CNRS 1859, D_partement de Biologie Cellulaire et Mol_culaire,
CEA Saclay, 91191 Gif sur Yvette, France
APStracts 5:0084F, 1998.
The effect of activation of the Ca2+ -sensing receptor on net Cl flux
(JCl) have been investigated on microperfused cortical (C) thick
ascending limb (TAL) from rat kidney. Increasing bath Ca2+ from 0.5
to 3mM or adding 200[mu]M of the specific Ca2+ -sensing receptor
agonist neomycin reduced basal as well as ADH-stimulated JCl by
27.7+/- 5.0% and 25.9 +/- 4.1% respectively. JCl remained unchanged
in time control tubules. The effect of neomycin/Ca2+ on JCl was
blocked by two protein kinase A inhibitors, H-9 or H-89, but not by a
protein kinase C inhibitor, GF 109203X, whether ADH was present or
not. Moreover, H-89 decreased basal JCl and prevented a further
effect of 3mM Ca2+. When JCl was increased by 8-bromo cAMP plus IBMX,
no effect of 3mM Ca2+ was observed. Inhibitors of phospholipase A2
and cytochrome P450 monooxygenase failed to modify the effect of 3mM
Ca2+ although these agents dampened significantly the inhibitory
effect of bradykinin on medullary TAL. It is concluded that
extracellular Ca2+ decreases basal and ADH-stimulated Cl reabsorption
in CTAL by inhibiting cAMP pathway, independently of protein kinase C
or phospholipase A2 stimulation.
Received 9 December 1997; accepted in final form 8 April 1998.
APS Manuscript Number F384-7.
Article publication pending Am. J. Physiol. (Renal Physiology).
ISSN 1080-4757 Copyright 1998 The American Physiological Society.
Published in APStracts on 24 April 1998