Evolution of stress activated Na+ K+ Cl- cotransport in bird red blood cells

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Birds are among the most active of vertebrates but our understanding of the mechanism by which birds achieve high levels of exercise are poorly known. This project investigates the role of a potassium transport mechanism in the red blood cell membrane of birds. High activity causes potassium loss from working muscles, which can lead to muscle fatigue. It is known that stress hormones like adrenaline cause an uptake of potassium into the red blood cells of some birds, which may allow the muscles to work more prolonged. We have found that this mechanism is missing in ostrich and others did not find it in chicken. Both birds are domesticated and have poor to non-existent flying abilities. We want to look at several more domesticated and wild species of birds with different exercise capacities, to assess the importance of stress-activated potassium transport in bird red blood cells. We then select four of these species and determine the molecular structure of the transport protein to understand how changes in its function during the evolution of birds have come about. This study will also help to better interpret disturbances in the potassium balance of birds. This is important because potassium balance is measured using blood plasma and stress hormones released during blood sampling will activate potassium uptake from the plasma into the red blood cells to a different degree in different bird species.