Studies on the labelling of brain phospholipids with radioactive phosphorus

Abstract

Methods were developed for determining the specific radioactivities of some of the phospholipids present in small samples of tissue labelled with p32. when a guinea pig brain dispersion is actively incorporating labelled phosphate into its lipids, there is no appreciable incorporation of p32 into phosphatidylethanolamine, phos-phatidylserine or sphingomyelin, while the renewal of lecithin P is very slow. Measurements suggest that diphosphoinositide P is renewed at an appreciable rate in actively respiring brain dispersions. Brain dispersions also synthesize uncharacterized material, soluble in fat solvents, which is probably acidic in nature and contains glycerophosphate as part of its molecule. The synthesis of this material is responsible for most of the incorporation of p32 into the lipids of a brain dispersion. The distr. of p32 in the lipids of a labelled brain dispersion was compared with that in the lipids of brain and liver slices and in the same tissues of the intact guinea pig.