Metabolism of exogenously applied fructose 1,6-bisphosphate in hypoxic vascular smooth muscle.
Exogenously administered fructose 1,6-bisphosphate reportedly protects ischemic or hypoxic tissue and facilitates metabolic recovery. The mechanism of action of exogenous fructose 1,6-bisphosphate has been an issue of considerable debate, since there is a lack of direct evidence that fructose 1,6-bisphosphate can cross the cell membrane and act as an intermediate in glycolysis. We synthesized [1,6-13C]fructose 1,6-bisphosphate and directly examined its cellular metabolism in hog carotid artery segments using 13C-nuclear magnetic resonance (NMR) spectroscopy. [1,6-13C]fructose 1,6-bisphosphate (2.1 mM) was metabolized by hog carotid artery during normoxia and hypoxia with a major metabolic product being [3-13C]lactate. The production of [3-13C]lactate was greater during hypoxia than during normoxia, indicating that fructose 1,6-bisphosphate metabolism responded to the energetic state of the tissue. We found that exogenously added fructose 1,6-bisphosphate at 2.1 mM did not significantly improve the ability of hypoxic hog carotid artery to maintain isometric force, whereas 20 mM fructose 1,6-bisphosphate did significantly, although modestly, improve isometric force maintenance. These results indicate that exogenously added fructose 1,6-bisphosphate is capable of entering cells and serving as a glycolytic intermediate.
Hardin
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CD
Department of Physiology, University of Missouri, Columbia 65212.
Roberts
T M
TM
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002247:Carbon Isotopes; D002339:Carotid Arteries / Q000378:metabolism; D004734:Energy Metabolism; D005635:Fructosediphosphates / Q000378:metabolism* / Q000494:pharmacology; D006019:Glycolysis; D066298:In Vitro Techniques; D007537:Isometric Contraction / Q000187:drug effects; D007773:Lactates / Q000378:metabolism; D019344:Lactic Acid; D009682:Magnetic Resonance Spectroscopy; D009131:Muscle, Smooth, Vascular / Q000378:metabolism*; D010100:Oxygen / Q000008:administration & dosage*; D013552:Swine
D002247:Carbon Isotopes; D005635:Fructosediphosphates; D007773:Lactates; D019344:Lactic Acid; D000255:Adenosine Triphosphate; C029063:fructose-1,6-diphosphate; D010100:Oxygen