AJP - Regulatory, Integrative and Comparative Physiology, Vol 253, Issue 6 877-R882, Copyright © 1987 by American Physiological Society
Role of atrial natriuretic peptide in natriuresis in volume-expanded rats
K. Kaneko, K. Okada, S. Ishikawa, T. Kuzuya and T. Saito
Department of Medicine, Jichi Medical School, Tochigi-ken, Japan.
Continuous intravenous infusion of rat atrial natriuretic peptide (rANP)
was carried out for 60 min in urethan-anesthetized rats. Plasma rANP (PANP)
levels during 0, 12.5, and 50 ng/min rANP infusion reached 20.9 +/- 3.4,
61.2 +/- 12.3, and 228 +/- 30.6 pg/ml, respectively. Urinary sodium
excretion (UNaV) remained unchanged during the 0 and 12.5 ng/min rANP
infusion. In contrast, the 50 ng/min rANP infusion resulted in a 5.6-fold
increase in UNaV without significant changes in plasma aldosterone levels
and glomerular filtration rate. Isotonic saline infusion (116
microliter/min for 60 or 120 min) caused a significant increase in UNaV.
UNaV in an experimental model of the syndrome of inappropriate antidiuretic
hormone secretion (SIADH) was 5.0 times greater than in control animals.
PANP levels in 60- or 120-min saline-infused and SIADH rats were 46.3 +/-
6.7, 39.0 +/- 9.0, and 35.6 +/- 3.2 pg/ml, respectively. These values were
significantly higher than control values but failed to achieve a level at
which natriuresis occurred during the infusion of rANP. These results
suggest that endogenous ANP may not play a critical role in the induction
of acute natriuresis in volume-expanded states, although it could be
partially involved in such a natriuretic response.
