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May 1971

Brain Uptake of Selenomethionine Se 75: I. Effects of Elevated Blood Levels of Methionine and Phenylalanine

Author Affiliations

Los Angeles
From the Research and Medical Services (Drs. Oldendorf and Sisson), and Neurology Section, Medical Service (Dr. Mehta), Wadsworth Hospital, Veterans Administration Center, and the Department of Neurology, UCLA School of Medicine (Drs. Oldendorf, Sisson, and Treciokas), Los Angeles.

Arch Neurol. 1971;24(5):423-430. doi:10.1001/archneur.1971.00480350057006

Uptake of selenomethionine Se 75 after intravenous injection in rat was studied in brain, pancreas, plasma, muscle, scalp, and skull. Selenomethionine Se 75 enters rat brain by a rate-limited process with a free exchange at low blood concentrations. Acute preloading with intravenously administered nonradioactive L-methionine or L-phenylalanine results in a reduction of brain uptake of selenomethionine Se 75. Phenylalanine is a more effective inhibitor than methionine. Measurable inhibition of brain uptake of selenomethionine Se 75 is demonstrated at lower plasma levels of phenylalanine than commonly found in clinical phenylketonuria. Bidirectionality of carrier mediated exchange of selenomethionine Se 75 between blood and brain was demonstrated by ventriculocisternal perfusion studies in rabbits. The gamma emissions of selenomethionine Se 75 may be useful in clinical studies of blood brain barrier (BBB) penetration by amino acids which share the same carrier mechanism facilitating BBB passage of selenomethionine Se 75.

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