GLUCOSE KINETICS IN NEONATAL ELEPHANT SEALS DURING POSTWEANING APHAGIA

Authors

  • Edward O. Keith,

    1. Institute for Marine Science, University of California, Santa Cruz, California 95064
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    • 1

      Department of Biochemistry and Molecular Biology (R629), University of Miami Medical School, P.O. Box 016129, Miami, Florida 33101.

  • Charles L. Ortiz

    1. Institute for Marine Science, University of California, Santa Cruz, California 95064
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Abstract

Northern elephant seal (Mirounga angustirostris)pups undergo extended periods of terrestrial aphagia after weaning and exhibit a paradoxical fasting hyperglycemia. To investigate the details of glucose metabolism during this period, reversible and irreversible radiotracers were used to determine the body mass of glucose, and rates of glucose turnover, recycling, and oxidation in fasting seal pups. A typical 75 kg pup has a glucose mass of about 4.5 g (60 mg/kg), and a blood glucose concentration of about 174 mg/dl. Blood glucose removal rate was about 30 grams per day (17 mg/kg · h-1), but less than 2.5% of this glucose was oxidized, contributing less than 1% of the total metabolic rate. About 20% of the glucose pool was removed from the blood per hour, yielding a turnover time in the vascular space of about five hours. Most glucose removed from the blood was returned to the blood by recycling. Such recycling may contribute to mechanisms which prolong survival during fasting, such as high rates of triacyclglycerol turnover, synthesis of new protein pools, low ketone levels, and the Cori cycle which is important during diving.

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