In vivo utilization of [3-14C]acetoacetate for lipid and amino acid synthesis in the 15-day-old chick.

1. The utilization of different concentrations of acetoacetate for the in vivo synthesis of lipids and amino acids has been studied in brain, spinal cord, liver, small intestine and kidney of 15-day-old chicks. Both lipid and amino acid synthesis increased in an almost linear fashion with precursor concentration in the five tissues mentioned. 2. Lipid synthesis was very high in spinal cord, followed in decreasing order by brain, small intestine, liver and kidney. At the highest concentration assayed (48 mM) the main lipids synthesized were triglycerides in liver (75%) and kidney (52%) and cholesterol in brain (47%), spinal cord (47%) and small intestine (42%). 3. Amino acid synthesis from acetoacetate did not vary markedly among the five organs, although brain and spinal cord showed higher rates at the maximal concentrations of precursor. Glutamate was always the main amino acid formed.