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Increased metabolism of infused 1-methylxanthine by working muscle


Youd, JM and Newman, JMB and Clark, MG and Appleby, GJ and Rattigan, S and Tong, CYA and Keske, MAV, Increased metabolism of infused 1-methylxanthine by working muscle, Acta Physiologica Scandinavica, 166, (4) pp. 301-308. ISSN 0001-6772 (1999) [Refereed Article]

DOI: doi:10.1046/j.1365-201x.1999.00572.x


Exogenous substrates for capillary endothelial enzymes have potential as markers for changes in capillary recruitment (albeit nutritive flow). The metabolism of infused 1-methylxanthine (1-MX) to 1-methylurate (1-MU) by capillary endothelial xanthine oxidase of the constant-flow perfused rat hindlimb was shown previously to decrease with oxygen uptake (V̇(o2)) when nutritive flow was decreased. In the present study, the metabolism of 1-MX was investigated under conditions when V̇(o2) and nutritive flow are known to increase during muscle contraction. The constant-flow red blood cell-perfused rat hindlimb at 37°C was used with sciatic nerve stimulation, and perfusate samples from whole hindlimb and working muscles taken for analysis of oxygen, lactate, 1-MX and 1-MU. Flow to muscle was assessed separately using fluorescent microspheres and was found to increase 2.3-fold to the working muscles while flow to the non-working leg muscles decreased to compensate. The activity of xanthine oxidase of whole muscle extracts was not altered by contraction. Samples from the vein draining the working muscles, and microsphere measurements of flow, indicated increased V̇(o2) (5.5-fold to 249.2 ± 43.1 μmol h-1 g-1, P < 0.001), and 1-MX conversion (2.5-fold to 1.87 ± 0.25 μmol h-1 g-1, P < 0.01) (SEM are shown). It is concluded that as 1-MX metabolism parallels V̇(o2), this substrate may be a useful indicator of changes in capillary (nutritive) surface area in muscle.

Item Details

Item Type:Refereed Article
Research Division:Biological Sciences
Research Group:Zoology
Research Field:Animal physiology - systems
Objective Division:Health
Objective Group:Clinical health
Objective Field:Clinical health not elsewhere classified
UTAS Author:Youd, JM (Miss Joanne Maree Youd)
UTAS Author:Newman, JMB (Dr John Newman)
UTAS Author:Clark, MG (Professor Michael Clark)
UTAS Author:Appleby, GJ (Mr Geoffrey Appleby)
UTAS Author:Rattigan, S (Professor Stephen Rattigan)
UTAS Author:Tong, CYA (Mr Chung Ying Alex Tong)
UTAS Author:Keske, MAV (Dr Michelle Keske)
ID Code:17129
Year Published:1999
Web of Science® Times Cited:17
Deposited By:Biochemistry
Deposited On:1999-08-01
Last Modified:2000-06-21

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