Cerebral lactate metabolism in near-term fetal sheep

Am J Physiol. 1995 Oct;269(4 Pt 2):R938-42. doi: 10.1152/ajpregu.1995.269.4.R938.


The present study was designed to see if lactate can cross the blood-brain barrier of the near-term fetal sheep and replace glucose as an oxidative substrate during normoglycemia and acute insulin-induced hypoglycemia. Cerebral uptake of glucose, oxygen, lactate, and [14C]lactate as well as cerebral production of 14CO2 were measured under three conditions: 1) normoglycemia-normolactemia, 2) acute hypoglycemia-normolactemia, and 3) hypoglycemia-steady-state hyperlactemia. Although uptake of tracer [14C]lactate was consistent, there was no net uptake of unlabeled lactate during either normoglycemia or hypoglycemia. When arterial lactate concentration was raised from 2.2 +/- 0.5 to 3.3 +/- 0.4 (SE) mM by sodium lactate infusion, however, lactate was taken up. Comparison of cerebral [14C]lactate uptake with 14CO2 production indicated that the principal metabolic fate of lactate is oxidation. At increased concentrations, exogenous lactate accounted for approximately 7% of cerebral oxygen consumption. This study demonstrates that lactate crosses the blood-brain barrier of the near-term fetal sheep, is oxidized, and at elevated concentrations can partially replace glucose as an oxidative substrate during acute hypoglycemia.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Blood Glucose / metabolism
  • Brain / embryology*
  • Female
  • Fetus / metabolism*
  • Glucose / metabolism
  • Lactates / blood
  • Lactates / metabolism*
  • Lactic Acid
  • Oxygen Consumption
  • Pregnancy
  • Sheep


  • Blood Glucose
  • Lactates
  • Lactic Acid
  • Glucose