Estimating In Vitro Mitochondrial Oxygen Consumption During Muscle Contraction and Recovery:
A Novel Approach that Accounts for Diffusion
A deconvolution algorithm,
based on a Bayesian statistical framework and smoothing spline technique,
is applied to reconstructing input functions
from noisy measurements in biological systems.
Deconvolution is usually ill-posed. However,
placing a Bayesian prior distribution on the input function
can make the problem well-posed.
Using this algorithm and a computational model
of diffusional oxygen transport in an
approximately cylindrical muscle
(about 0.5 mm diameter and 10 mm long mouse leg muscle),
the time course of muscle oxygen uptake and mitochondrial oxygen consumption,
both during isometric twitch contractions
(at various frequencies) and the recovery period,
is estimated from polarographic measurements of
oxygen concentration on the muscle surface.
An important feature of our experimental protocol is
the availability of data for the apparatus characteristics.
From these time courses,
the actual mitochondrial consumption rates
during resting and exercise states can be estimated.
Mitochondrial oxygen consumption rate increased during
stimulation to a maximum steady state value approximately
5 times of the resting value of
0.63 nanomoles per second per gram-wet weight
for the stimulation conditions studied.
Diffusion slowed the kinetic responses to the contraction
but not the steady state fluxes during the stimulation interval.