AJP - Regulatory, Integrative and Comparative Physiology, Vol 265, Issue 3 596-R601, Copyright © 1993 by American Physiological Society
Autonomic modulation of ovine fetal responses to atrial natriuretic factor infusion
L. A. Bayer, C. Y. Cheung and R. A. Brace
Department of Reproductive Medicine, University of California at San Diego, La Jolla 92093-0802.
The aim of this study was to determine whether the autonomic nervous system
modulates the cardiovascular, endocrine, and/or urinary responses to atrial
natriuretic factor (ANF) infusion in the fetus. We infused ANF
intravenously for 30 min into chronically catheterized, late-gestation
sheep fetuses with autonomic blockade and compared the responses to those
in autonomically intact fetuses. During the infusions, plasma ANF
concentration increased similarly in the blocked and intact fetuses.
Arterial pressure decreased by 2 mmHg in both groups, but the decrease
occurred earlier in the blocked fetuses. Heart rate was significantly
decreased by an average of 15 beats/min in the blocked compared with the
intact fetuses. Plasma protein concentration decreased in the blocked
fetuses compared with a rise in the intact fetuses. In the blocked fetuses,
the restoration of blood volume to normal during the postinfusion period
occurred earlier. In the blocked animals, low doses of ANF produced a
diuresis, whereas high doses did not increase urine flow; the opposite
responses occurred in the intact group. Plasma arginine vasopressin (AVP)
concentration increased during the infusion only in the blocked animals.
The fetal venous pressure, plasma renin activity, and norepinephrine
responses were similar in both groups. These data suggest that the
autonomic nervous system may play a role in modulating the fetal arterial
pressure, heart rate, blood volume, plasma protein concentration, AVP, and
urine flow responses to ANF. Thus the autonomic nervous system appears to
significantly modulate multiple responses to ANF in the late-gestation
ovine fetus.
