Physiological Mechanisms of Anoxic Tolerance

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9420017 Jackson The object of this investigation is to understand how a specially adapted vertebrate animal, the freshwater turtle, is able to survive long periods without oxygen. Based on this knowledge, the long-term goal is to uncover fundamental principles of cellular and organismal function related to this problem. Several experimental approaches will be utilized. First, at the whole animal level, the distribution and excretion of key body fluid substances, lactic acid, CO2 and chloride ion will be determined using injected radioactively-labelled compounds. These compounds are all important in determining acid-base balance during anoxia and these experiments will clarify aspects of the important homeostatic function of blood pH regulation in these animals. Second, heart function in these animals will be studied because of the usual sensitivity of this organ to anoxia. Mechanical properties of small strips of cardiac muscle will be studied under conditions that simulate the anoxic state of the living animal, utilizing known changes in blood pH, ion concentrations, and catecholamine levels in our test solutions. Third, the response of skeletal muscle to long-term anoxia will be studied both in the intact animal and in isolated pieces of muscle using the technique of magnetic resonance spectroscopy. Dr. Jackson's object in these experiments is to assess the cellular energetics, the capacity to do work, and the recovery from activity in the muscles of this animal in the absence of oxygen. The remarkable characteristics of an animal specialist such as the turtle and its organ systems make it an ideal preparation for understanding basic principles of cellular metabolism and energetics in response to anoxia and acidosis. Of broader significance is understanding how adaptations revealed at the cell or organ system level incorporate into the integrative behavior of the intact animal. ***