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Vascular control of resting metabolism in muscle

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Steen, J. T (1996) Vascular control of resting metabolism in muscle. PhD thesis, University of Tasmania.

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Abstract

Vascular Control of Resting Metabolism in Muscle
Whilst it is generally accepted that the metabolic rate of muscle will determine its own blood
flow by autoregulation the reverse relationship of blood flow controlling metabolism is less
understood. Investigations by Clark and colleagues (Clark et al. 1995) suggest the existence of two
different vascular systems in the perfused rat hindlimb. One of these systems appears to be nutritive
for muscle while the other system appears to behave as a functional shunt. When flow is selectively
directed through either of these systems by vasoconstrictors or vasodilators profound metabolic
changes are observed. One set of vasoconstrictors, Type A, can double the resting metabolic rate of
the perfused hindlimb while the other set, Type B, can halve the resting metabolic rate of the
perfused hindlimb.
The aim of the present thesis was to obtain further evidence for two discretely different
vascular systems in muscle and to investigate the histological nature of these two different vascular
systems .. A secondary aim of the thesis was to assess the control of selective vascular recruitment
over key metabolic pathways such as lactate metabolism and glycolysis, glycerol metabolism lipolysis
and respiration.
The first group of experiments provided further evidence for two different vascular systems
in the hindlimb. One of these experiments used fluorescent microspheres to measure blood flow
distribution between muscle groups and methyl-xanthine (an indicator of vascular recruitment) to
assess the degree of nutritive flow. Another set of experiments provided fluorescent dye-tracing
evidence for vessels supplying septa and tendons being non-nutritive conduits for the Type B
response.
Investigations into vasoconstrictor and flow-rate control of lactate uptake and release by
muscle showed that both Type A norepinephrine (ie., concentrations of norepinephrine below I µM)
and increased-flow, stimulated lactate release from the perfused hindlimb. However, when 10 mM
lactate was added to the perfusion medium to stimulate lactate uptake increased flow was found to
increase uptake while Type A norepinephrine decreased lactate uptake. These data indicate a
mechanistic difference between flow and vasoconstrictor-stimulated metabolism. Glycerol release
from the hindlimb was also regulated by vasoconstrictors suggesting a vascular control of lipid
metabolism. However, no concurrent decrease in respiratory quotient or increase in fatty acid release
was found during Type A stimulation, thus suggesting a vascular control of the fatty acid reesterification cycle.

Item Type: Thesis (PhD)
Copyright Holders: The Author
Copyright Information:

Copyright the Author - The University is continuing to endeavour to trace the copyright
owner(s) and in the meantime this item has been reproduced here in good faith. We
would be pleased to hear from the copyright owner(s). 1996.

Additional Information:

Thesis (Ph.D.)--University of Tasmania, 1997. Includes bibliographical references. Contents: Serotonin inhibition of 1-methylxanthine metabolism indicative of enhanced non-nutritive flow in muscle -- Evidence for vessels supplying septa and tendons acting as functional shunts in the perfused hindlimb -- Vasoconstrictor-mediated control of lactate metabolism -- Influence of vasoconstrictors on fat metabolism of perfused hindlimb

Date Deposited: 03 Feb 2015 03:25
Last Modified: 11 Mar 2016 05:55
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