Premium
Oxygen Exchange Profile in Rat Muscles of Contrasting Fibre Types
Author(s) -
Behnke Brad J.,
McDonough Paul,
Padilla Danielle J.,
Musch Timothy I.,
Poole David C.
Publication year - 2003
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2002.035915
Subject(s) - chemistry , oxygen , skeletal muscle , blood flow , fibre type , steady state (chemistry) , anatomy , zoology , medicine , biology , organic chemistry
To determine whether fibre type affects the O 2 exchange characteristics of skeletal muscle at the microcirculatory level we tested the hypothesis that, following the onset of contractions, muscle comprising predominately type I fibres (soleus, Sol, 86 % type I) would, based on demonstrated blood flow responses, exhibit a blunted microvascular P O2 ( P O2,m , which is determined by the O 2 delivery ( Q̇ O2 ) to O 2 uptake ( V̇ O2 ) ratio) profile (assessed via phosphorescence quenching) compared to muscle of primarily type II fibres (peroneal, Per, 84 % type II). P O2,m was measured at rest, and following the rest‐contractions (twitch, 1 Hz, 2–4 V for 120 s) transition in Sol ( n = 6 ) and Per ( n = 6 ) muscles of Sprague‐Dawley rats. Both muscles exhibited a delay followed by a mono‐exponential decrease in P O2,m to the steady state. However, compared with Sol, Per demonstrated (1) a larger change in baseline minus steady state contracting P O2,m (Δ P O2,m ) (Per, 13.4 ± 1.7 mmHg; Sol, 8.6 ± 0.9 mmHg, P < 0.05 ); (2) a faster mean response time (i.e. time delay (TD) plus time constant (τ); Per, 23.8 ± 1.5 s; Sol, 39.6 ± 4.3 s, P < 0.05 ); and therefore (3) a greater rate of P O2,m decline (Δ P O2,m /τ; Per, 0.92 ± 0.08 mmHg s −1 ; Sol, 0.42 ± 0.05 mmHg s −1 , P < 0.05 ). These data demonstrate an increased microvascular pressure head of O 2 at any given point after the initial time delay for Sol versus Per following the onset of contractions that is probably due to faster Q̇ O2 dynamics relative to those of V̇ O2 .