This project will combine animal physiology with biophysics and biochemistry in order to examine oxygen transport and consumption from whole animal to subcellular levels during the prolonged, spontaneous breath-holds of elephant seals during sleep. Unique adaptations in these animals include enhanced oxygen storage and exquisite regulation of heart rate, blood flow and tissue metabolic rates. The physiological processes and biochemical mechanisms underlying these adaptations are relevant to the basic principles of oxygen transfer within tissues as well as to the remarkable diving abilities of seals and whales. A variety of minimally- and non-invasive techniques, including blood/tissue sampling, blood flow measurements, and nuclear magnetic resonance imaging/spectroscopy, will allow study of these seals while they sleep undisturbed. This will allow: 1) examination of the regulation of heart rate, cardiac output and muscle blood flow throughout the ten-minute breath-holds of these seals, 2) measurement of the rate of blood oxygen depletion throughout the breath-hold, 3) examination of blood-to-muscle oxygen transfer as the blood oxygen level decreases, 4) determination of the oxygen desaturation rate of myoglobin - the oxygen storage protein in muscle, 5) examination of metabolic regulation in muscle, as reflected in the depletion of the high-energy phosphate, phosphocreatine, and the formation of lactate, and 6) examination of the mobility of the myoglobin molecule within the muscle cell.
