UTILISATION OF KETONE BODIES BY RAT BRAIN HOMOGENATES

Publisher Summary Ketone bodies (KB) become quantitatively important substrates for brain metabolism in the rat when their concentration in the blood rises. The enhanced utilization of KB could be a consequence both of an increased transport through the blood brain barrier and of an enzymic adaptation of brain cells for the activation and breakdown of acetoacetate and D-3-hydroxybutyrate. This chapter discusses a study to examine the utilization of KB by rat brain homogenates. The utilization of AcAc was maximal in the presence of L -malate, valinomycin, and Mg. ATP inhibited the oxidation of AcAc but not of pyruvate in this system. Indirect evidence was obtained that ATP interferes with the mitochondrial uptake of AcAc. After the incubation of adult brain homogenate with [3- 14 C]AcAc and removal of excess substrate, more than 70% of the label was found in the acid soluble fraction, mainly in Krebs cycle intermediates and amino acids. 14 CO 2 production accounted for less than 25%. No incorporation of label into protein or lipid fractions was detected. It is found that the utilization of KB for the biosynthesis of lipids was only observed in homogenates of neonatal rats.