AJP - Regulatory, Integrative and Comparative Physiology, Vol 257, Issue 3 580-R587, Copyright © 1989 by American Physiological Society
Fetal cardiovascular, endocrine, and fluid responses to atrial natriuretic factor infusion
R. A. Brace, L. A. Bayer and C. Y. Cheung
Department of Reproductive Medicine, University of California, San Diego, La Jolla 92093.
The purpose of this study was to determine the effects of atrial
natriuretic factor (ANF) in the fetus and to explore the interactions among
the fetal cardiovascular, endocrine, and fluid responses to ANF. In 12
chronically catheterized fetal sheep at 130 +/- 1 (SE) days gestation, ANF
was infused intravenously for 30 min at 14-300 ng.min-1.kg-1. Fetal
arterial plasma ANF concentration increased by 174 to 5,410 pg/ml from a
preinfusion value of 163 +/- 13 pg/ml. The clearance of ANF from the
circulation was 122 +/- 28 ml.min-1.kg-1 and the half-life was 0.46 +/-
0.07 min. When plasma ANF was greater than 2,000 pg/ml, fetal arterial
pressure decreased, venous pressure increased transiently, and heart rate
was unchanged. Plasma arginine vasopressin (AVP) concentration and plasma
renin activity (PRA) increased with high ANF concentrations, while
norepinephrine concentrations were unaffected. Fetal blood volume decreased
in all fetuses, and urine flow increased significantly but not in every
fetus. Blood and urine osmolalities did not change. On terminating the
infusion, venous pressure and urine flow decreased below control, while
blood volume and arterial pressure remained reduced. Plasma AVP
concentration increased further, and this was accompanied by an increase in
urine osmolality. Thus the most consistent effect of ANF in the fetus was a
reduction in blood volume, which was independent of urine flow changes.
Other cardiovascular, endocrine, and fluid responses to ANF as well as
interactions among them appeared to occur largely at supraphysiological
concentrations and may be secondary to the changes in blood
volume.(ABSTRACT TRUNCATED AT 250 WORDS)
