Paper Information

Title: 

ALDOSTERONE STIMULATES A RAPID INCREASE IN URINARY SODIUM EXCRETION BUT NOT URINARY HCO3- EXCRETION NOR PH IN THE ANAESTHETISED RAT

Type: SPEECH
Author(s): KHAJAVIRAD A.A.F.,BALMENT R.,ASHTON N.
 
 
 
Name of Seminar: IRANIAN CONGRESS OF PHYSIOLOGY AND PHARMACOLOGY
Type of Seminar:  CONGRESS
Sponsor:  PHYSIOLOGY AND PHARMACOLOGY SOCIETY, MASHHAD UNIVERSITY OF MEDICAL SCIENCE
Date:  2007Volume 18
 
 
Abstract: 

Aldosterone appears to exert rapid effects via non-genomic mechanisms in addition to its classical genomic actions. Contrary to its well known genomic action on urinary sodium reabsorption and potassium excretion, we have previously shown that aldosterone causes a rapid increase in urinary sodium excretion but has no effect on potassium output in vivo (Rad et al. 2002). Aldosterone has also been shown to inhibit bicarbonate absorption via a non-genomic pathway in the thick ascending limb in vitro. Accordingly, the aim of this study was to determine whether aldosterone stimulates rapid changes in urinary bicarbonate excretion and urine pH in vivo. Under Intraval anaesthesia (100 mg kg-1) male Sprague Dawley rats received euvolaemic fluid replacement of spontaneous urine output using a servo-controlled system. After a 3 h equilibration period, control urine and plasma samples were taken, following which half of the animals received aldosterone (42 pmol min-1) for 1 hour before returning to dextrose alone for the final hour. Aldosterone infusion had no effect on urine flow rate, but resulted in a significant (P<0.05), rapid increase in urinary sodium excretion. Urinary bicarbonate excretion and urine pH did not change over the hour of aldosterone infusion by comparison with control animals. While these data do not provide evidence that aldosterone exerts a rapid effect on urinary pH and bicarbonate excretion in vivo, this possibility cannot be excluded due to potential modification or buffering of the final urine downstream of the thick ascending limb. The natriuresis observed following aldosterone infusion confirms our previous observation.

 
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