Journal of Applied Physiology, Vol 42, Issue 4 643-649, Copyright © 1977 by American Physiological Society
Extraction and radioimmunoassay of urinary aldosterone in the rat
H. D. Battarbee, G. E. Farrar and J. K. Braley
Results from studies of the rat renin-angiotensin-aldosterone axis have
been inconsistent and oftentimes conflicting among various laboratories and
have led many investigators to regard the rat as a poor model with which to
study this sytem. Many of these discrepancies have been shown to be due to
the use of anesthetic agents in experimental protocols. Studies of
unanesthesized animals indicate that the rat bears a remarkable resemblance
to other mammalian species, but unfortunately the unanesthesized rat lends
itself well only to acute studies, usually requiring killing the animal.
Herein is described a method which permits the estimation of aldosterone
excretory rates in intact, nonstressed, unanesthesized rats. The method is
based upon the excretion and radioimmunoassay of urinary "acid-labile" or
3-oxo-conjugate of aldosterone. It is very sensitive, permitting the
detection of less than 10 pg of aldosterone conjugate in extracted samples,
and when compared to the double-isotope-dilution method, it is relatively
inexpensive and much less tedious. Radioimmunoassays of rat urinary
aldosterone excretion during 14.75 days of sodium depletion reflected a
brisk increase in urinary excretion rate after day 2 and a concomitant
reduction in sodium excretion that bears a remarkable resemblance to the
excretory patterns described for man.
