Control of proximal tubule acidification by the endothelium of the
peritubular capillaries.
Amorena, Carlos, Marcelo T. De Alvear, and Ariel F. Castro.
Instituto de Investigaciones Cardiol[acute]ogicas, Facultad de
Medicina, Universidad de Buenos Aires, 2270 (1122) Buenos Aires,
Argentina
APStracts 3:0364R, 1996.
Cyclic GMP, a nitric oxide mediator, stimulates Na+/H+ exchange in
brush-border vesicles of the renal cortex. The aim of the present
work was to test whether the endothelium of the peritubular
capillaries modulates the rate of proximal luminal acidification
through the release of endothelium derived nitric oxide (EDNO).
Perfusion of the tubule lumen with dibutyryl cGMP increased net
proton flux (JH). Two agents that elicit EDNO production, bradykinin
(BK) and carbamylcholine (Cch), increased JH when added to the
peritubular capillary perfusate. Bradykinin did not affect JH when
the peritubular capillaries and the lumen were perfused with Na-free
solution. Methylene blue (MB) and NG-nitro-L-arginine methyl ester
(L-NAME) blocked the elevation in JH by Cch, and also decreased basal
JH. Bradykinin increased cGMP content of isolated proximal convoluted
tubules, but only if they were co-incubated with endothelial cells.
This effect of BK was blocked by L-NAME. The results suggest that the
endothelium of the peritubular capillaries affects proximal tubule
acidification through changes of cGMP in proximal tubule cells,
probably via stimulation of Na+/H+ exchanger.
Received 28 September 1995; accepted in final form 3 September
1996.
APS Manuscript Number R610-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 5 November 1996