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Incorporation and utilization of [3-13C]lactate and [1,2-13C]acetate by rat skeletal muscle.

Authors :
Bertocci LA
Lujan BF
Source :
Journal of applied physiology (Bethesda, Md. : 1985) [J Appl Physiol (1985)] 1999 Jun; Vol. 86 (6), pp. 2077-89.
Publication Year :
1999

Abstract

Skeletal muscle can utilize many different substrates, and traditional methodologies allow only indirect discrimination between oxidative and nonoxidative uptake of substrate, possibly with contamination by metabolism of other internal organs. Our goal was to apply 1H- and 13C-nuclear magnetic resonance spectroscopy to monitor the patterns of [3-13C]lactate and [1,2-13C]acetate (model of simple carbohydrates and fats, respectively) utilization in resting vs. contracting muscle extracts of the isolated perfused rat hindquarter. Total metabolite concentrations were measured by using NADH-linked fluorometric assays. Fractional oxidation of [3-13C]lactate was unchanged by contraction despite vascular endogenous lactate accumulation. Although label accumulated in several citric acid cycle (CAC) intermediates, contraction did not increase the concentration of CAC intermediates in any muscle extracts. We conclude that 1) the isolated rat hindquarter is a viable, well-controlled model for measuring skeletal muscle 13C-labeled substrate utilization; 2) lactate is readily oxidized even during contractile activity; 3) entry and exit from the CAC, via oxidative and nonoxidative pathways, is a component of normal muscle metabolism and function; and 4) there are possible differences between gastrocnemius and soleus muscles in utilization of nonoxidative pathways.

Details

Language :
English
ISSN :
8750-7587
Volume :
86
Issue :
6
Database :
MEDLINE
Journal :
Journal of applied physiology (Bethesda, Md. : 1985)
Publication Type :
Academic Journal
Accession number :
10368376
Full Text :
https://doi.org/10.1152/jappl.1999.86.6.2077