Cardiac enzyme activities in fetal and adult pregnant and non
-pregnant sheep exposed to high-altitude hypoxemia.
Ohtsuka, Teruo, and Raymond D. Gilbert.
Division of Perinatal Biology, Department of Physiology and
Obstetrics and Gynecology, Loma Linda University, School of Medicine,
Loma Linda, CA 92350
APStracts 2:0245A, 1995.
We measured pyruvate kinase (PK), citrate synthase (CS) and lactate
dehydrogenase (LDH) activities in the right and left ventricles of
fetal, maternal, and non-pregnant adult sheep exposed to high
altitude (3,820 m) for 112 days and compared them to control groups
of animals kept at sea level. Enzymes were assayed by the
spectrophotometric appearance of reaction products specific to each
enzyme and activity was expressed as [mu]mol/min/g wet weight of
tissue. In control sheep citrate synthase activity was significantly
higher in both ventricles of the pregnant and non-pregnant adult
compared to the fetus. However, lactate dehydrogenase and pyruvate
kinase activities were only higher in the left ventricle of the non
-pregnant adult compared to the fetus. Long-term hypoxemia
significantly increased LDH activities in fetal (57%, 53%), pregnant
adult (29%, 27%), and non-pregnant adult (25%, 24%) right and left
ventricles, respectively. Citrate synthase activities also increased
in fetal (89%, 97%), pregnant adult (43%, 39%), and non-pregnant
adult (46%, 48%) right and left ventricles, respectively. However, PK
activity was not affected by altitude in any group of animals. In the
fetal heart which uses lactate as its primary metabolic fuel, these
enzyme changes may help enhance aerobic energy production during
hypoxemia. In the adult heart which relies on free fatty acids, as
well as glucose, for energy production, the significance of these
enzyme changes is less clear.
Received 4 November 1990; accepted in final form 22 May 1995.
APS Manuscript Number A1139-4.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 6 July 1995.