AJP - Regulatory, Integrative and Comparative Physiology, Vol 256, Issue 1 284-R289, Copyright © 1989 by American Physiological Society
Atrial peptide potentiates renal responses to volume expansion in conscious dogs
C. H. Metzler and D. J. Ramsay
Department of Physiology, School of Medicine, University of California, San Francisco 94143.
Experiments were performed to compare the renal responses to atrial peptide
infusion in conscious dogs with normal and expanded extracellular fluid
volumes to test the hypothesis that the renal responses to atrial peptide
infusions are dependent on the prevailing fluid and electrolyte status in
the animal. Atrial peptide-(99-126) was infused intravenously in doses of
either 0, 5, 25, or 100 ng.kg-1.min-1 in conscious dogs prepared with
chronic catheters in the femoral artery and vein and the urinary bladder.
In dogs with normal extracellular fluid volume, atrial peptide caused small
increases in urinary sodium excretion with the high physiological (25
ng.kg-1.min-1) and pharmacological (100 ng.kg-1.min-1) doses. Urine volume
and potassium excretion were increased only at the highest pharmacological
dose. In contrast, atrial peptide infusion in dogs that were volume
expanded by infusion of hypertonic saline showed dramatic, dose-dependent
increases in sodium excretion and urine flow with all doses tested. The
low, physiological dose of atrial peptide (5 ng.kg-1.min-1) increased
sodium excretion and urine flow rate in volume-expanded dogs more than the
pharmacological dose in normal dogs (n = 4). These results demonstrate that
the renal responses to atrial peptide infusion are potentiated in dogs that
are volume expanded and suggest that under conditions where atrial peptide
secretion would be enhanced, small changes in plasma atrial peptide
concentration can have significant effects on renal function.
