AJP - Endocrinology and Metabolism, Vol 246, Issue 4 350-E355, Copyright © 1984 by American Physiological Society
Catecholamine physiology in ovine fetus. II. Metabolic clearance rate of epinephrine
S. M. Palmer, G. K. Oakes, R. W. Lam, C. J. Hobel and D. A. Fisher
This study measured the metabolic clearance rate (MCR) of epinephrine (E)
in 13 chronically catheterized fetal lambs between 120 and 145 days
gestation. The E-MCR was determined by a constant infusion method at an E
infusion rate of 0.1 microgram/kg estimated fetal wt. Fetal and maternal
arterial blood samples were taken for measurements of catecholamine levels,
pH, blood gases, and glucose. There was a significant positive correlation
between gestational age and E-MCR (r = 0.87, P less than 0.001). The E
production rate in fetuses less than 132 days (n = 6) (1,234 +/- 301
pg/min) was not significantly different from fetuses greater than or equal
to 132 days (n = 7) (1,195 +/- 242). Catecholamine infusion resulted in a
decrease in pH from a control value of 7.37 +/- 0.01 to 7.31 +/- 0.01 by 15
min of infusion, but there were no significant changes in fetal heart rate
or blood pressure. The mean fetal plasma glucose concentration increased
45% above base line at 15 and 20 min and 65% above base line by 30 min of
catecholamine infusion. After 60 min of infusion plasma norepinephrine (NE)
increased from 380 +/- 60 to 520 +/- 75 pg/ml and plasma dopamine from 100
+/- 20 to 240 +/- 50 pg/ml (both P less than 0.05). These results indicate
that E-MCR increases with maturation in the absence of a change in basal E
production.
