Determination of local brain glucose level with [14c]
methylglucose: effects of glucose supply and demand.
Dienel, Gerald A., Nancy F. Cruz, Keiji Adachi, Louis Sokoloff, and
James E. Holden.
Laboratory of Cerebral Metabolism, National Institute of Mental
Health, Bethesda, MD, U.S.A. 20892, Department of Medical Physics,
University of Wisconsin Medical School,Madison, WI, U.S.A. 53706
APStracts 4:0157E, 1997.
Methylglucose can be used to assay brain glucose levels because the
equilibrium brain:plasma distribution ratio for methylglucose
(Ce*/Cp*) is quantitatively related to brain (Ce) and plasma (Cp)
glucose contents. The relationship between Ce and Ce*/Cp* predicted
by Michaelis-Menten kinetics has been experimentally confirmed when
glucose utilization (CMRglc) is maintained at normal, resting levels
and Cp is varied in conscious rats. Theoretically, however, Ce and
Ce*/Cp* should change when CMRglc is altered and Cp is held constant;
their relationship in such conditions was, therefore, examined
experimentally. Drugs were applied topically to brains of conscious
rats with fixed levels of Cp to produce focal alterations in CMRglc,
and Ce and Ce*/Cp* were measured. Plots of Ce as a function of
Ce*/Cp* for each Cp produced straight lines; their slopes decreased
as Cp increased. The results confirm that a single theoretical
framework describes the relationship between Ce and Ce*/Cp* as either
glucose supply or demand is altered over a wide range and validate
the use of methylglucose to estimate local Ce under abnormal
conditions.
Received 12 February 1997; accepted in final form 7 July 1997.
APS Manuscript Number E063-7.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 24 July 1997