ISSN:
1471-4159
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Medicine
Notes:
Abstract: 3-O-Methyl-d-glucose (methylglucose) is often used to study blood-brain barrier transport and the distribution spaces of hexoses in brain. A critical requirement of this application is that it not be chemically converted in the tissues. Recent reports of phosphorylation of methylglucose by yeast and heart hexokinase have raised questions about its metabolic stability in brain. Therefore, we have re-examined this question by studying the metabolism of methylglucose by yeast hexokinase and rat brain homogenates in vitro and rat brain, heart, and liver in vivo. Commercial preparations of yeast hexokinase did convert methylglucose to acidic products, but only when the enzyme was present in very large amounts. Methylglucose was not phosphorylated by brain homogenates under conditions that converted 97% of [U-14C]glucose to ionic derivatives. When [14C]methylglucose, labeled in either the methyl or glucose moiety, was administered to rats by an intravenous pulse or a programmed infusion that maintained the arterial concentration constant and total 14C was extracted from the tissues 60 min later, 97–100% of the 14C in brain, 〉99% of the 14C in plasma, and 〉90% of that in heart and liver were recovered as unmetabolized [14C]methylglucose. Small amounts of 14C in brain (1–3%), heart (3–6%), and liver (4–7%) were recovered in acidic products. Plasma glucose levels ranging from hypoglycemia to hyperglycemia had little influence on the degree of this conversion. The distribution spaces for methylglucose were found to be 0.52 in brain and heart and 0.75 in liver.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1471-4159.1990.tb04588.x
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