High altitude environments challenge the physiology of
mammals mainly due to hypoxic conditions. As a response to this, many mammals
show molecular adaptations e.g. by mutations in the genes encoding the hemoglobins.
This can result in an increase O2 affinity (and thereby a
leftshifted O2 dissociation curve) which will enhance the pulmonary
loading of O2. However, the shift can also hamper the O2 unloading
process to the metabolic tissue. To elucidate this trade-off between loading and
unloading a numerical computer model was made in the program Insigt maker based
on the organism, deer mouse (Peromyscus
maniculatus). The numerical solution was calculated by the Runge-Kutta
method. A time step (dt) of 0.00001 was chosen, as the results were independent
of dt at this value. This was tested by investigating the residual values of an
interval of dt around 0.00001. The model showed how the trade-off is expressed
at different altitudes and how the degree of advantages/disadvantages varies.
Based on the model it can be suggested that the trade-off is beneficial, when
the hypoxia is severe at high altitude. This is consistent with previously
findings.
