AJP - Renal Physiology, Vol 252, Issue 1 26-F31, Copyright © 1987 by American Physiological Society
Chronic effects of vasopressin on fluid volume distribution in conscious dogs
D. C. Merrill and A. W. Cowley Jr
Previous studies have suggested that acute elevations of arginine
vasopressin (AVP) may result in an extravascular to intravascular shift of
fluid independent of any change in total body H2O (TBW). The present
studies examined the chronic influence of elevated AVP on fluid volume
distribution in five splenectomized, sodium-deprived conscious dogs (avg
body wt = 18.9 +/- 0.7 kg). During 4 days of continuous intravenous AVP
infusion (0.36 ng X kg-1 X min-1), the computerized average 24-h total body
weight was maintained within 110 g of the control value by means of a
sensitive servo-controlled scale device. Urine flow and urine osmolality
averaged 335 +/- 52 ml/day and 637 +/- 36 mosmol/kg during the preinfusion
period and changed to levels averaging 151 +/- 14 and 1,377 +/- 121 with
elevated AVP (P less than 0.05). Chromium-51-labeled red cell volume (51Cr
RBC), plasma volume (Evans blue), TBW (3H2O), calculated total blood volume
(using 51Cr RBC and Hct), and mean arterial pressure averaged 22 +/- 1
ml/kg, 54 +/- 7 ml/kg, 0.62 +/- 0.04 l/kg, 68 +/- 3 ml/kg, and 99 +/- 3
mmHg, respectively, during the control period and remained unchanged during
the AVP infusion period. Plasma protein, sodium, and osmolality averaged
6.4 +/- 0.1 g/dl, 145.7 +/- 0.8 meq/l, and 295.0 +/- 1.5 mosmol/kg during
the preinfusion period and also remained unchanged with elevated AVP. We
conclude from the present studies that AVP has minimal or no chronic
influence on internal volume redistribution.
