Metabolism of ketone bodies by ovine brain in vivo.

Ketosis was produced by intravenous infusion (5 mmol/kg per h) of [3-14C]acetoacetate (sp act 0.5 muCi/mmol) into fed and 7-day-fasted sheep. Changes in arterial and sagittal sinus blood samples. During acetoacetate infusion, there was a significant increase in ketone body uptake (P less than 0.001) and conversion to 14CO2 in both fed and fasted sheep. Changes in arterial concentrations and cerebral removal of various metabolites were investigated by simultaneous collection of arterial and sagittal sinus blood samples. During acetoacetate infusion, there was a significant increase in ketone body uptake (P less than 0.001) and conversion to 14CO2 in both fed and fasted sheep when compared to control periods (saline infusion). The percent conversion of ketone bodies to 14CO2 was slightly higher in fasted sheep (22%) compared to fed sheep (18%). Blood glucose and free fatty acid concentrations were decreased, but there was a significant increase in blood lactic acid and lactic acid production by the brain. The plasma insulin concentration was increased significantly both in fed and fasted animals. These results indicate that ovine brain can utilize ketone bodies irrespective of nutritional state. In addition, ketone bodies stimulated the production of lactate by ovine brain.