
antidiuretic properties of chlorothiazide
in diabetes insipidus dogs
chlorothiazide was found to decrease
urine volume and increase urine con-
centration in diabetes insipidus dogs.
there was no change in gfr, rpf,
tmpah, plasma volume, extracellular
fluid or total body water.  the one con-
sistent altered function was a decrease
in "free water" clearance.  diazoxide and
mercuhydrin were not antidiuretic.  it is
believed that the antidiuretic action is
dependent on the chlorothiazide-induced
saluresis.  although the mechanism of
this antidiuresis has not been clearly de-
fined, it seems best explained by postu-
lating a decrease in filtrate reaching the
distal nephron (giving a decreased final
urine volume) coupled with inhibition of
solute reabsorption in the distal tubule
(preventing the selective reabsorption of
solute in the distal tubule that is nor-
mally seen, accounting for the increase
in urine concentration).  the possible
role of the mineralocorticoids in the
antidiuretic response to chlorothiazide
therapy was investigated in diabetes in-
sipidus and adrenalectomized dogs.  ad-
ministration of sodium-retaining steroids
to diabetes insipidus dogs did not re-
produce the urinary changes associated
with chlorothiazide therapy.  in addition,
the antidiuretic response to chlorothia-
zide was not altered by adrenalectomy
or spironolactone administration.  there-
fore, the presence of the sodium-retain-
ing steroids are not essential for the anti-
diuretic response of chlorothiazide in
diabetes insipidus.
