AJP - Regulatory, Integrative and Comparative Physiology, Vol 269, Issue 6 1455-R1461, Copyright © 1995 by American Physiological Society
Glucose and oxygen metabolism in the fetal foal during late gestation
A. L. Fowden and M. Silver
Physiological Laboratory, Cambridge, United Kingdom.
With the use of [U-14C]glucose tracer methodology, the rates of umbilical
uptake, utilization, oxidation, and production of glucose were determined
in nine chronically catheterized fetal foals in the fed state between 268
and 325 days of gestation (term approximately 335 days). At the same time,
the rates of umbilical O2 and lactate uptake were measured in all nine
fetuses by Fick principle. The mean fetal rates of umbilical glucose
uptake, glucose utilization, and CO2 production from glucose carbon were
36.9 +/- 2.5, 36.4 +/- 1.7, and 117.7 +/- 17.4 mumol.min-1.kg fetal body
wt-1, respectively (n = 9). Endogenous glucose production was therefore
negligible in the fetal foal in the fed state. Production of CO2 from
glucose carbon accounted for 40.9 +/- 6.5% of the umbilical O2 uptake,
which averaged 292 +/- 15 mumol.min-1.kg-1 (n = 9). No significant changes
in fetal glucose or O2 metabolism were observed with increasing gestational
age. The rates of umbilical glucose uptake, glucose utilization, and CO2
production from glucose carbon (P < 0.01), but not the rate of umbilical
O2 uptake (P > 0.05), were positively correlated with the fetal blood
glucose level. There was a significant umbilical lactate uptake in the
fetuses older than 290 days (12.3 +/- 4.1 mumol.min-1.kg-1, n = 5, P <
0.05) but not in the younger animals (6.2 +/- 9.6 mumol.min-1.kg-1, n = 4,
P > 0.05). Hence, glucose is used for both oxidative and nonoxidative
metabolism in utero and is a major, although not the sole, oxidative
substrate in the fetal foal during late gestation.
