The placenta releases branched-chain keto acids into the umbilical and uterine circulations in the pregnant sheep.
There was net uptake of branched-chain keto acids by the fetus from the umbilical circulation. Mean fetal uptake of the 3 keto acids 2-keto isovalerate, 2-keto isocaproate and 2-keto methylvalerate was 1.8 mumol/min per kg of fetus. The concentrations in the umbilical vein for these keto acids were 10.9 +/- 3.8 microM (mean +/- SD: 2-keto isovalerate), 19.7 +/- 6.1 microM (2-keto isocaproate) and 14.8 +/- 5.3 microM (2-keto methylvalerate) respectively. The coefficients of extraction for the same keto acids were 17.2%, 16.8% and 11.9% respectively. Fetal uptakes (both mumol/min and mumol/min per kg fetus) were positively correlated with umbilical supply. There were concentration gradients across the placenta, with fetal concentration: maternal concentration ratios of 3.3 +/- 1.5 for 2-keto isovalerate, 2.1 +/- 0.8 for 2-keto isocaproate and 1.3 +/- 0.6 for 2-keto methylvalerate. The net release of 2-keto acids into the umbilical circulation may conserve the carbon skeleton of branched-chain amino acids for fetal metabolism and growth. In the uterine circulation there was not a consistent pattern of release from or uptake by the uteroplacental tissues. It is suggested that branched-chain keto acids may contribute to fetal growth or energy metabolism.
Smeaton
T C
TC
Department of Obstetrics & Gynaecology, University of Adelaide, South Australia.
Owens
J A
JA
Kind
K L
KL
Robinson
J S
JS
D000818:Animals; D001775:Blood Circulation / Q000187:drug effects; D005260:Female; D005312:Fetal Blood / Q000032:analysis*; D005333:Fetus / Q000378:metabolism; D045782:Hemiterpenes; D007651:Keto Acids / Q000032:analysis / Q000378:metabolism*; D008431:Maternal-Fetal Exchange; D010920:Placenta / Q000378:metabolism*; D011247:Pregnancy; D012756:Sheep; D014599:Uterus / Q000098:blood supply* / Q000378:metabolism
D045782:Hemiterpenes; D007651:Keto Acids; C016211:alpha-keto-beta-methylvaleric acid; C001505:alpha-ketoisovalerate; C013082:alpha-ketoisocaproic acid