AJP - Regulatory, Integrative and Comparative Physiology, Vol 253, Issue 4 561-R567, Copyright © 1987 by American Physiological Society
Cardiovascular and fluid responses to atrial natriuretic factor in sheep fetus
R. A. Brace and C. Y. Cheung
Department of Reproductive Medicine, University of California, San Diego, La Jolla 92093.
Presently little is known about the effects of atrial natriuretic factor
(ANF) in the fetus. In this study we explored the effects of ANF on
vascular pressures and fluid dynamics in the chronically catheterized sheep
fetuses averaging 133 days gestation (term = 145-150 days). Under resting
conditions plasma ANF concentration was positively correlated with fetal
heart rate (P less than 0.001) and was not correlated with arterial
pressure, venous pressure, or plasma osmolality. The weight-normalized
fetal urine flow rate correlated positively with ANF concentration (P less
than 0.01). After a bolus injection of 8 micrograms/kg of synthetic human
ANF into the inferior vena cava, fetal arterial pressure decreased by 2
mmHg and remained at this level for 60 min, venous pressure was unchanged,
and heart rate increased transiently by 15 beats/min. Urine flow rate
increased to 250% of control 5 min after the injection and returned to
control at 20 min even though ANF was four times control levels. Fetal
blood volume decreased significantly by 5% within 10 min and remained low
for 60 min. This decrease in blood volume was greater than the increase in
urine flow. A kinetic analysis revealed that ANF disappearance from the
plasma could not be adequately characterized with a single rate constant
due to exchange between plasma and interstitial fluid.(ABSTRACT TRUNCATED
AT 250 WORDS)
