Rat acetoacetate decarboxylase: its role in the disposal of 4C-ketone bodies by the fetus.

21-day pregnant rats show high tissular and plasmatic acetone concentrations when submitted to a 48-hr fast. This rise is, in fact, associated with an enhanced placental and fetal acetoacetate decarboxylase activity. We propose that acetone formation by the fetus could be a mechanism for pH maintenance and that acetoacetate decarboxylase can play a significant role in the handling of 4C-ketone bodies under conditions in which the substrate concentration cannot easily be controlled by other physiological mechanisms.