AJP - Renal Physiology, Vol 258, Issue 4 768-F774, Copyright © 1990 by American Physiological Society
Comparative effects of diuretics and atrial peptide in chronic caval dogs
M. Levy
Department of Physiology, McGill University, Montreal, Quebec, Canada.
Anesthetized chronic caval dogs with ascites were given atrial natriuretic
peptide (ANF) at 75 ng.kg-1.min-1 iv and were characterized as to
natriuretic response [n = 21; urinary excretion rate of Na (UNaV): 28-362
mu eq/min] or lack of response (n = 14; UNaV: 0-10 mu eq/min). Sixteen
normal dogs showed an increment in UNaV between 38 and 288 mu eq/min
following the same dose of ANF. Both caval "responders" and "nonresponders"
were equivalent with regard to pre- and post-ANF hemodynamics and renal
function. When various diuretic agents (glucagon, acetazolamide,
furosemide, thiazide, amiloride) were administered, equivalent natriuretic
responses were obtained between both groups of caval dogs and the controls.
An acute saline load (7% body wt), however, produced a greater natriuresis
in controls than in caval dogs, but in this latter group the response was
similar in responders and nonresponders. When six caval dogs each were
initially pretreated with either amiloride or ANF, and then treated with a
second agent, an additive natriuretic effect was obtained. These results
suggest that tubular resistance to diuretics in caval dogs is unique to
ANF, and this peptide appears to act at an additional Na transport site
separate from amiloride-inhibitable channels.
