title: Perinatal changes in myocardial metabolism in lambs.
abstract: BACKGROUND
  Lactate accounts for a third of myocardial oxygen consumption before and in the first 2 weeks after birth. It is unknown how the remainder of myocardial oxygen is consumed. Glucose is thought to be important before birth, whereas long-chain fatty acids (LC-FA) are the prime substrate for the adult. However, the ability of the myocardium of the newborn to use LC-FA has been doubted.
  
  
  RESULTS
  We measured the myocardial metabolism of glucose and LC-FA with [U-(13)C]glucose and [1-(13)C]palmitate in chronically instrumented fetal and newborn lambs. In fetal lambs, myocardial oxidation of glucose was high and that of LC-FA was low. Glucose and LC-FA accounted for 48+/-4% and 2+/-2% of myocardial oxygen consumption, respectively. In newborn lambs, oxidation of glucose decreased, whereas oxidation of LC-FA increased. Glucose and LC-FA accounted for 12+/-3% and 83+/-19% of myocardial oxygen consumption. To test whether near-term fetal lambs could use LC-FA, we increased the supply of LC-FA with a fat infusion. In fetal lambs during fat infusion, the oxidation of LC-FA increased 15-fold. Although the oxidation of LC-FA was still lower than in newborn lambs, the contribution to myocardial oxygen consumption (70+/-13%) was the same as in newborn lambs.
  
  
  CONCLUSIONS
  These data show that glucose and lactate account for the majority of myocardial oxygen consumption in fetal lambs, whereas in newborn lambs, LC-FA and lactate account for the majority of myocardial oxygen consumption. Moreover, we showed that the fetal myocardium can use LC-FA as an energy substrate.
authors.affiliation: Division of Pediatric Cardiology, Department of Pediatrics, Beatrix Children's Hospital, Groningen, The Netherlands. b.bartelds@planet.nl
authors.forename: B
authors.initials: B
authors.lastname: Bartelds
authors.forename: H
authors.initials: H
authors.lastname: Knoester
authors.forename: G B
authors.initials: GB
authors.lastname: Smid
authors.forename: J
authors.initials: J
authors.lastname: Takens
authors.forename: G H
authors.initials: GH
authors.lastname: Visser
authors.forename: L
authors.initials: L
authors.lastname: Penninga
authors.forename: F R
authors.initials: FR
authors.lastname: van der Leij
authors.forename: G C
authors.initials: GC
authors.lastname: Beaufort-Krol
authors.forename: W G
authors.initials: WG
authors.lastname: Zijlstra
authors.forename: H S
authors.initials: HS
authors.lastname: Heymans
authors.forename: J R
authors.initials: JR
authors.lastname: Kuipers
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D002250:Carbon Radioisotopes; D004734:Energy Metabolism; D005260:Female; D005947:Glucose / Q000378:metabolism; D006321:Heart / Q000196:embryology* / Q000254:growth & development; D009206:Myocardium / Q000378:metabolism*; D010101:Oxygen Consumption / Q000502:physiology; D019308:Palmitic Acid / Q000378:metabolism; D011247:Pregnancy; D012756:Sheep
chemical_list: D002250:Carbon Radioisotopes; D019308:Palmitic Acid; D005947:Glucose