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Nutritive and non-nutritive blood flow in muscle

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Youd, Joanne Maree (2000) Nutritive and non-nutritive blood flow in muscle. PhD thesis, University of Tasmania.

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Abstract

The idea that two vascular routes exist within, or closely associated with, skeletal
muscle (nutritive and non-nutritive blood flow) dates back to early last century
(1900's). Recent work in the past decade or two in our laboratory as well as
contributions by other researchers has shed more light on the anatomical nature and
functional role of the skeletal muscle vasculature and shown how changes to the blood
flow distribution within skeletal muscle occur during different physiological states,
e.g. exercise and insulin resistance.
Until recently, an effective and non-invasive method to measure the proportion of
nutritive to non-nutritive blood flow within muscle did not exist. Such a method
would prove invaluable as a general technique to assess the blood flow distribution
within skeletal muscle and would have definite clinical application. Recent studies
from this research group have focussed on investigating the use of 1-methylxanthine
(1-MX) metabolism as an indicator of nutritive flow, or capillary recruitment, within
skeletal muscle. It has been shown that capillary recruitment increases during insulin
infusion in vivo and this increase is blocked when acute insulin resistance is induced
by a methyl serotonin, an agent known to direct muscle blood flow to the non-nutritive
route.
This project had two main aims. Firstly, to further investigate the use of the 1-MX
method in insulin resistant rats in vivo (tumour necrosis factor a, TNF), and in hindimb
perfusion (sciatic nerve stimulation and sciatic nerve severance). Secondly, to develop
a new technique for the measurement of nutritive and non-nutritive blood flow based
on laser Doppler flowmetry (LDF), in the hope that concordance between the two
methods (1-MX and LDF) would be attained.
Under conditions of insulin resistance in vivo induced by 3 hour infusion of TNF ( +/-
insulin), 1-MX metabolism (capillary flow) and total femoral blood flow were
decreased as compared with insulin alone. In rat hindlimb perfusion, sciatic nerve
stimulated rats (causing contraction of the calf muscle group) resulted in increased 1-MX metabolism by the working muscles. Sciatic nerve severance, a rat model of
insulin resistance, did not cause any changes in 1-MX metabolism and so the insulin
resistance observed in this model did not appear to be a caused by changes in blood
flow distribution.
Changes seen in LDF signal under a number of conditions were similar to the changes
seen in 1-MX metabolism. During rat hindimb blood perfusion, vasoconstrictors
known to increase and decrease nutritive and non-nutritive blood flow in skeletal
muscle produced corresponding changes in laser Doppler signal. In addition, in vivo
where insulin is known to increase capillary recruitment as measured by 1-MX
metabolism, the LDF signal increased. Epinephrine, which produces large increases in
total blood flow to the hindlimb but does not stimulate glucose uptake, produced no
change in capillary recruitment or LDF.
Overall, the study was successful and the two main aims were accomplished.
Application of the 1-MX method was extended and concordance with LDF was
achieved. Both methods, with certain limitations and assumptions would appear to be
capable of detecting changes in capillary recruitment or nutritive blood flow in skeletal muscle.

Item Type: Thesis (PhD)
Keywords: Musculoskeletal system, Muscles, Musculoskeletal system, Muscles, Blood flow
Copyright Holders: The Author
Copyright Information:

Copyright 2000 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).

Additional Information:

Thesis (Ph.D.)--University of Tasmania, 2000. Includes bibliographical references

Date Deposited: 04 Feb 2015 23:27
Last Modified: 24 Aug 2016 04:10
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