Fig. 4.

Plasma catecholamine levels in deer mice native to low altitude and high altitude following acclimation to normoxia or hypoxia. A: schematic shows the catecholamine biosynthesis pathway within chromaffin cells of the adrenal medulla leading up to vesicular release into the circulation (14). B–D: in mice acclimated to normoxic conditions, the plasma concentrations of dopamine (B) and norephinephrine (C) were similar in lowland (▲) and highland (∇) populations, but levels of epinephrine (D) were higher in lowlanders (n = 8) compared with highlanders (n = 14). All differences in catecholamine levels between populations were abolished after mice were acclimated to hypoxic conditions (hypoxic lowlanders, n = 6; hypoxic highlanders, n = 8). *Pairwise differences between populations within an acclimation environment; †significant interaction between population and acclimation environment in 2-way ANOVA. Error bars are ± SE.