Abstract Radioactive acetyl groups and lipids are produced from dl-[5-14C]glutamate. Degradation studies indicate that approximately 90 per cent of the radioactivity is localized in the original carboxyl groups of the two carbon unit. Since these results are shown not to be due to a 14CO2 fixation, it is concluded that the oxoglutarate shunt as an acetyl group transport system is functional in brain.

The highest ratio of fatty’acid activity/CO2 activity in this pathway is found in the newborn rat brain and steadily decreases with development. This pattern is observed with incubations of brain slices with labelled glutamate or citrate and is similar to the changes observed in the activity of the citrate cleavage enzyme with brain maturation.

In contrast to the previous studies with liver preparations, the conversion of [2-14C]- and [5-14C]glutamate to fatty acids is relatively small. This is particularly true during the period of maximal lipid synthesis.