Effect of hypoxemia on tissue glycogen content and glycolytic
enzyme activities in fetal sheep.
Stratford, L. L., and S. B. Hooper.
Department of Physiology, Monash University, Clayton, 3168,
Victoria, Australia
APStracts 3:0191R, 1996.
We have tested the hypothesis that prolonged fetal hypoxemia causes a
reduction in glycogenolytic enzyme activities and/or a depletion of
fetal glycogen stores. We compared the effects of short (4h) and
prolonged (24h) periods of reduced maternal uterine blood flow (RUBF)
on glycogen content, and on the activities of glucose-6-phosphatase
(G-6-Pase), glycogen phosphorylase (GPase) and glycogen synthase
(GSase) in selected fetal tissues. RUBF was reduced in 10 pregnant
sheep at 135 days of gestation (term 146d) for either 4h (n=5) or 24h
(n=5); 5 other fetuses were used as controls. During RUBF, fetal SaO2
was decreased from 61.6+/-3.9% to 22.0+/-1.4% at 4h and to 26.7+/
-1.2% at 24h. Hepatic glycogen content was significantly reduced at 4h
of RUBF, but was not reduced further at 24h. Fetal liver GPase
(active and total enzyme activity) and G-6-Pase activities were
reduced at 4h of RUBF but tended to return towards control values at
24h. Similarly, hepatic GSase activity tended to decrease at 4h of
RUBF although the reduction was not quite significant (p=0.08). We
conclude that RUBF causes a reduction of fetal glycogen stores and a
reduction in G-6-Pase and GPase activity at 4h. Fetal tissue glycogen
contents were not reduced further at 24h, compared with 4h of RUBF,
which indicates that fetal glycogenolysis is reduced during this
time, probably due to the inhibition of GPase and G-6-Pase. It is not
known why the activities of these enzymes are reduced during
prolonged RUBF, when circulating epinephrine and norepinephrine
concentrations are high.
Received 23 August 1995; accepted in final form 1 May 1996.
APS Manuscript Number R527-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 28 May 96