In vivo13c nuclear magnetic resonance investigations of choline metabolism in rabbit brain

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Abstract
The metabolism of choline in rabbit brain was studied by the noninvasive approach of in vivo 13C NMR spectroscopy. 13C‐Enriched precursors were introduced into the brain. Surgery of the head skin was avoided through controlled localization of the surface coil. For long‐term accumulation studies in brain, repeated subcutaneous injections proved to be advantageous over other forms of application. The resorption kinetics was calculated to be zero order which suggests slow delivery from the subcutaneous depots. Choline metabolism was studied by two approaches: [N‐13CH3] choline and S‐[ 13CH3 ] methionine were administered separately to adult and myelinating rabbits (Days 5 to 32), respectively, over 4 weeks. [ N‐ 13CH3] Choline and the 13CH3 group of methionine were incorporated into lecithin and sphingomyelin of brain myelin. In vivo kinetic studies of the turnover of these labeled structures were carried out. Choline and methionine are readily transported through the blood‐brain barrier and utilized by the myelinating brain for the biosynthesis of its phospholipids.