AJP - Renal Physiology, Vol 253, Issue 5 969-F975, Copyright © 1987 by American Physiological Society
Atrial natriuretic peptide, right atrial pressure, and sodium excretion rate in the rat
T. A. Fried, M. A. Ayon, G. McDonald, A. Lau, T. Inagami and J. H. Stein
Department of Medicine, University of Texas Health Science Center, San Antonio 78284.
This study examined the relationship between right atrial pressure (RAP),
urine flow rate, sodium excretion rate, and plasma atrial natriuretic
peptide (ANP) levels after an acute Ringer expansion. Two groups of rats
had their RAP monitored and balloon catheters placed in their thoracic
inferior venae cavae. In one group the balloon remained deflated, and in
the second group the balloon was inflated during the volume expansion in an
attempt to prevent the rise in RAP. The peak RAP was 7.3 +/- 0.8 mmHg when
the balloon remained deflated and 3.5 +/- 0.6 mmHg in the group with the
balloon catheter inflated (P less than 0.005). The corresponding peak ANP
levels were 682 +/- 140 and 223 +/- 40 pg/ml. There was a significant
correlation between the peak RAP and ANP levels (r = 0.754; P less than
0.05). The inflation of the balloon catheter significantly decreased the
urine flow rate and the urine sodium excretion rate. A final group of
animals had 200 microliters of rabbit serum containing antibody to ANP
infused before the volume expansion. The antibody-treated animals had
significantly lower urine flow and sodium excretion rates than
nonantibody-treated control rats. We conclude that ANP is one of the
factors which allows the rat to excrete an acute Ringer expansion.
