Effect of norepinephrine on intracellular ph in the kidney p
roximal tubule: role of na+/(hco3-)n cotransport.
Abdulnour-Nakhoul, Solange, Raja N. Khuri, and Nazih L. Nakhoul.
Departments of Medicine and Physiology, Tulane University, School
of Medicine, New Orleans, LA 70112 and East Carolina University,
Greenville, NC 27858
APStracts 5:0061F, 1998.
We examined the effect of norepinephrine (NE) on intracellular pH
(pHi) and activity of Na+ (aiNa) in the isolated perfused kidney
proximal tubule of Ambystoma, using single barreled voltage and ion
selective microelectrodes. In control HCO3- Ringer, addition of 10-6
M NE to the bath (B) reversibly depolarized the basolateral membrane
potential (V1), the luminal membrane potential (V2) and the
transepithelial potential difference (V3) and increased pHi by
0.14(0.02. These effects were mimicked by isoproterenol but were
abolished after pretreatment with SITS or in the absence of CO2/HCO3-
. Removal of (B) Na+ depolarized V1 and V2., hyperpolarized V3 and
decreased pHi . These effects are largely mediated by the
electrogenic Na+/(HCO3-)n cotransporter. In the presence of NE, the
effects of Na+ removal on membrane PDs and the rate of change of pHi
were significantly smaller. Reducing bath [HCO3-] from 10 to 2 mM at
constant CO2 (pH 6.8), depolarized V1 and V2, decreased pHi and
lowered aiNa. These changes are also due to Na+/(HCO3-)n. In the
presence of NE, reducing bath [HCO3-] caused a smaller
depolarizations of V1 and V2 and the rate of pHi decrease was
significantly less. Our results indicate: 1) NE causes an increase in
pHi. 2) The NE-induced alkalinization is mediated by a SITS sensitive
and HCO3--dependent transporter on the basolateral membrane. 3) In
the presence of NE, the reduced effects caused by basolateral HCO3-
changes or Na+ removal, are indicative of an inhibitory effect of NE
on Na+/ (HCO3-)n cotransport.
Received 12 November 1997; accepted in final form 26 February
1998.
APS Manuscript Number F356-7.
Article publication pending Am. J. Physiol. (Renal Physiology).
ISSN 1080-4757 Copyright 1998 The American Physiological Society.
Published in APStracts on 9 March 1998