BERTING, J.I.*; KINSEY, S.T.; University of North Carolina Wilmington: The Response of Myoglobin Concentration to Chronic Hypobaric Hypoxia is Strain Specific in Mice

Myoglobin is the final mediator of oxygen flux from the atmosphere to the mitochondria in the oxygen delivery cascade, and is the only component of the cascade that is intracellular. Because myoglobin�s role is to maintain intracellular pO2 within a narrow range, its concentration might be expected to react to changes in the balance between supply of oxygen to the cell and the demand for oxygen by the cell. We have previously found that in inbred strains of mice, acclimation to hypoxia resulted in large changes in myoglobin concentration that differed in both magnitude and direction of change. However, inbred strains may have a limited range of phenotypic plasticity for some components of the oxygen delivery cascade due to a lack of genetic variability, which may necessitate relatively large fluctuations in myoglobin concentration in response to hypoxia. In contrast, outbred strains may be better able to co-adjust upstream components of the cascade in response to hypoxia. With this in mind, we hypothesized that the higher heterozygosity of outbred strains would result in smaller changes in myoglobin concentrations after acclimation to hypoxia. To address this we analyzed the concentration of myoglobin in the right ventricle, gastrocneumius, soleus, and extensor digitorum longus from the three outbred strains of mice: ICR, Swiss Webster, and CD-1. The results show that after acclimation to hypoxia, myoglobin concentrations in heart and skeletal muscle of these outbred strains have little variance. This may imply that given greater phenotypic plasticity, individual components of the oxygen delivery cascade, such as myoglobin, may not require substantial adjustment to meet the functional demand for oxygen.