Cerebral lactate metabolism in near-term fetal sheep .
Turbow, Robert M., Douglas Curran-Everett, William W. Hay, Jr, M.
Douglas Jones, Jr.
Division of Perinatal Medicine, Departments of Pediatrics and
Physiology, The University of Colorado School of Medicine, Department
of Pediatrics, The Children's Hospital, Denver, Colorado
APStracts 2:0196R, 1995.
The present study was designed to see if lactate can cross the blood
-brain barrier of the near-term fetal sheep and replace glucose as an
oxidative substrate during normoglycemia and acute insulin-induced
hypoglycemia. Cerebral uptake of glucose, oxygen, lactate and 14C
-lactate as well as cerebral production of 14CO2 were measured under
three conditions: normoglycemia/normolactemia, acute hypoglycemia/
normolactemia and hypoglycemia/steady-state hyperlactemia. Although
uptake of tracer 14C-lactate was consistent, there was no net uptake
of unlabelled lactate during either normoglycemia or hypoglycemia.
When arterial lactate concentration was raised from 2.2 +/- 0.5 (+/-
SEM) to 3.3 +/- 0.4 mM by sodium lactate infusion, however, lactate
was taken up. Comparison of cerebral 14C-lactate uptake with 14CO2
production indicated that the principal metabolic fate of lactate is
oxidation. At increased concentrations, exogenous lactate accounted
for approximately 7% of cerebral oxygen consumption. This study
demonstrates that lactate crosses the blood brain barrier of the
near-term fetal sheep, is oxidized, and at elevated concentrations
can partially replace glucose as an oxidative substrate during acute
hypoglycemia.
Received 18 January 1995; accepted in final form 30 May 1995.
APS Manuscript Number R44-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 18 July 1995.