9728794 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, and why other animals are unable to do this. The long-term goal is to discover fundamental principles of cellular and organismal function related to this adaptation. Several experimental approaches will be utilized. First, the role of the turtle's shell and skeleton in enabling the turtle to withstand the large buildup of lactic acid during long-term anoxia will be investigated. Dr. Jackson has found that the shell both releases buffer compounds into the blood and serves as a storage site for lactate. He will determine whether the skeleton does the same. The role of the shell in lactate storage is a new finding and he will explore this further in the turtle and will also look for bone or hard tissue lactate uptake in other animals subject to sizable increases in circulating lactate. He postulates that this may be an important acid-base regulatory mechanism in many animals. In addition, the ionic exchanges between the turtle shell and extracellular fluid will be studied in preparations of powdered shell incubated with solutions of different pH and ionic composition. Whole body ionic exchanges during anoxia will also be studied in intact animals to further characterize the contribution of the shell and body fluids to acid-base regulation. He will continue his work on the adaptation of turtle heart to anoxia and acidosis using nuclear magnetic resonance spectroscopy and a computer-activated lever system to study perfused working hearts and ventricular muscle strips, respectively. A particular goal of this grant period is to compare responses in the anoxia-tolerant turtle heart with hearts from anoxia-intolerant species, such as trout.
