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Increased metabolism of infused 1-methylxanthine by working muscle

Version 2 2024-06-04, 10:48
Version 1 2017-03-29, 12:03
journal contribution
posted on 2024-06-04, 10:48 authored by JM Youd, JMB Newman, MG Clark, GJ Appleby, S Rattigan, ACY Tong, Michelle KeskeMichelle Keske
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 (VO2) when nutritive flow was decreased. In the present study, the metabolism of 1-MX was investigated under conditions when VO2 and nutritive flow are known to increase during muscle contraction. The constant-flow red blood cell-perfused rat hindlimb at 37 degrees 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 VO2 (5.5-fold to 249.2 +/- 43.1 micromol h-1 g-1, P < 0.001), and 1-MX conversion (2.5-fold to 1.87 +/- 0.25 micromol h-1 g-1, P < 0.01) (SEM are shown). It is concluded that as 1-MX metabolism parallels VO2, this substrate may be a useful indicator of changes in capillary (nutritive) surface area in muscle.

History

Journal

Acta physiologica Scandinavica

Volume

166

Pagination

301-308

Location

England

ISSN

0001-6772

eISSN

1748-1716

Language

eng

Publication classification

CN.1 Other journal article

Issue

4

Publisher

Wiley