The metabolism of phospholipids in mouse brain slices.

1. Slices of mouse brain grey matter were incubated with [(32)P]phosphate and [1-(14)C]acetate. Doubly labelled phospholipids were extracted from subcellular fractions prepared from the slices in a mixture of metabolic inhibitors, under conditions where there was negligible change in radioactive labelling during the preparation. Two tissue fractions were studied in detail; one contained a high proportion of mitochondria and the other was mainly microsomal. 2. In all tissue fractions the highest incorporations of both [(32)P]phosphate and [1-(14)C]acetate occurred into phosphatidylcholine. 3. After incubation for 1hr., the (32)P/(14)C ratios for phosphatidylcholine, phosphatidylethanolamine and phosphatidic acid in the mitochondrial fraction were similar to those in the microsomal fraction. 4. The (32)P/(14)C ratios were similar in phosphatidylcholine and phosphatidylethanolamine and much lower than those in phosphatidic acid and phosphatidylinositol.