Physiological Basis of Metabolism and Activity: The Cardiopulmonary Physiology of Digestion and Exercise

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This research investigates cardiopulmonary (heart, lung, and circulatory) function during elevated metabolism. Previously, physiologists could only induce substantially elevated metabolism in ecotherms by exercising them. Hence, it was not possible to separate the elements of cardiopulmonary function associated with elevated metabolism per se from those elements specific to exercise. Recent experiments with reptiles have demonstrated that digestion may increase metabolism to levels equal to those during maximal activity. Elevated metabolism stimulated by exercise induces hyperventilation. Elevated metabolism stimulated by digestion induces hypoventilation. The investigators will undertake experiments to determine the physiological basis for hypoventilation during digestion. In other experiments, the investigators will measure gas exchange, blood gas and acid-base status, cardiac shunting and blood flow distribution simultaneously. They will compare animals subjected to various combinations of resting, exercising, feeding, and fasting to determine how the conflicting demands of digestion and exercise are resolved. This research will permit an understanding of the match between supply and demand in metabolic gas exchange and the identification of those elements that are stereotyped and state-independent from those that are flexible and state-dependent.