Get access

Brain Arachidonic Acid Incorporation and Precursor Pool Specific Activity During Intravenous Infusion of Unesterified [3H]Arachidonate in the Anesthetized Rat

Authors

  • Kazushige Washizaki,

    1. Laboratory of Neurosciences, National Institute on Aging, National Institutes of Health, Bethesda, Maryland, U.S.A.
    Search for more papers by this author
    • The present address of Dr. K. Washizaki is Department of Neurology, Faculty of Medicine, University of Tokyo, Hongo 7-3-1, Bunkyo, Tokyo 113, Japan.

  • Quentin R. Smith,

    1. Laboratory of Neurosciences, National Institute on Aging, National Institutes of Health, Bethesda, Maryland, U.S.A.
    Search for more papers by this author
  • Stanley I. Rapoport,

    1. Laboratory of Neurosciences, National Institute on Aging, National Institutes of Health, Bethesda, Maryland, U.S.A.
    Search for more papers by this author
  • A. David Purdon

    Corresponding author
    1. Laboratory of Neurosciences, National Institute on Aging, National Institutes of Health, Bethesda, Maryland, U.S.A.
    Search for more papers by this author

Address correspondence and reprint requests to Dr. A. D. Purdon at Laboratory of Neurosciences, National Institute on Aging, National Institutes of Health, Building 10, Room 6C-103, Bethesda, MD 20892, U.S.A.

Abstract

Abstract: Brain fatty acid incorporation into phospholipids can be measured in vivo following intravenous injection of fatty acid tracer. However, to calculate a cerebral incorporation rate, knowledge is required of tracer specific activity in the final brain precursor pool. To determine this for one tracer, unesterified [3H]arachidonate was infused intravenously in pentobarbital-anesthetized rats to maintain constant plasma specific activity for 1–10 min. At the end of infusion, animals were killed by microwave irradiation and analyzed for tracer specific activity and concentration in brain phospholipid, neutral lipid, and lipid precursor, i.e., unesterified arachidonate and arachidonoyl-CoA, pools. Tracer specific activity in brain unesterified arachidonate and arachidonoyl-CoA rose quickly (t1/2 < 1 min) to steady-state values that averaged <5% of plasma specific activity. Incorporation was rapid, as >85% of brain tracer was present in phospholipids at 1 min of infusion. The results demonstrate that unesterified arachidonate is rapidly taken up and incorporated in brain but that brain phospholipid precursor pools fail to equilibrate with plasma in short experiments. Low brain precursor specific activity may result from (a) dilution of label with unlabeled arachidonate from alternate sources or (b) precursor pool compartmentalization. The results suggest that arachidonate turnover in brain phospholipids is more rapid than previously assumed.

Ancillary