Contribution of acetoacetate to the synthesis of cholesterol and fatty acids in regions of developing rat brain in vivo.

(3)H(2)O and [3-(14)C]acetoacetate were injected i.p. into developing rats (5-50 days of age). After 2 h the brains were dissected into 6 parts. The incorporation of (3)H and (14)C into total fatty acids and into cholesterol in these 6 parts and in the spinal cord was measured. The data were analysed to evaluate the developmental patterns of the synthesis of fatty acids and cholesterol in various parts of the rat CNS and to compare the contribution of acetoacetate to these processes. Our results indicate (1) a large variation between CNS regions in the rates of lipid synthesis as well as in the developmental patterns; highest activities were found in the spinal cord during the third postnatal week, whereas the activities in cortical areas were much lower during all stages of development; (2) a constant ratio between the amounts of label incorporated into lipid fractions from [3-(14)C]acetoacetate and from (3)H(2)O, indicating that acetoacetate contributes to a similar extent to lipid synthesis in all parts of the developing rat CNS; (3) a similar preference in the use of acetoacetate for cholesterogenesis as compared to lipogenesis in all parts of the CNS of suckling rats; (4) a marked increase of this preference after weaning of the pups.