AJP - Regulatory, Integrative and Comparative Physiology, Vol 269, Issue 1 57-R63, Copyright © 1995 by American Physiological Society
Renal response of roosters with diabetes insipidus to infusions of arginine vasotocin
M. Brummermann and E. J. Braun
Department of Physiology, University of Arizona, Tucson 85724, USA.
In a strain of white Leghorn chicken with symptoms of hereditary diabetes
insipidus (DI) and with elevated circulating levels of the antidiuretic
hormone arginine vasotocin (AVT), we investigated whether the defect is
based on nonfunctional endogenous AVT or on a diminished renal response to
AVT. DI chickens responded to hyposmotic infusions with a higher urine flow
and lower glomerular filtration rate (GFR) than healthy control birds.
Urine osmolality, fractional excretion, and clearance of sodium were lower
in DI birds while potassium values were similar in both groups. Hence, the
high urine flow rates of the DI birds were predominantly based on a water
diuresis. When infused with AVT, the GFR and the urine flow of the control
birds decreased and urine osmolality increased, showing both glomerular and
tubular effects of AVT. During AVT infusion, the GFR of DI birds increased,
urine flow decreased only moderately, and urine osmolality was half that of
the control birds. In control birds, the clearance of sodium was unchanged,
whereas that of potassium decreased. In DI birds, which experienced a
strong natriuresis, the clearance of both sodium and potassium increased.
These data suggest that the sensitivity of the DI birds to AVT is reduced
at the tubular level. The AVT-induced increase in GFR may be related to
vascular effects of high AVT doses, added to the already high basal AVT
level of the DI birds, in combination with an imbalance in the function of
V1 and V2 receptor subtypes in these chickens.
