AMINO-ACID-UPTAKE BY THE FETAL OVINE HINDLIMB UNDER NORMAL AND EUGLYCEMIC HYPERINSULINEMIC STATES

As part of an effort to establish the contribution of different fetal organs to fetal amino acid metabolism, we measured in nine sheep fetus es the uptake of 27 amino acids by the hindlimb under normal condition s and conditions of euglycemic hyperinsulinemia. The fetal hindlimb is representative of nonvisceral tissues, which in the mature fetus acco unt for similar to 70% of fetal weight and 30% of fetal O-2 consumptio n. In the normal condition, there was a significant uptake of 21 amino acids for a net total nitrogen uptake of 132 +/- 21 mg N.day(-1).100 g(-1). The amino acids taken up by the fetal limb included alanine and glutamine. In addition, the fetal limb had significant glutamate and serine uptakes. Because glutamate flows from fetus to placenta and the re is no fetal uptake of maternal serine, this indicates production an d interorgan transport of these amino acids within the fetus. Insulin infusion significantly decreased the arterial concentration of every a mino acid with the exception of cystathionine and significantly increa sed limb blood flow and glucose uptake. It significantly increased the limb uptake of alanine, asparagine, glycine, isoleucine, methionine, and tyrosine, decreased the uptake of aspartate, and produced no signi ficant change in the net total nitrogen uptake, which remained similar to control (137 +/- 16 mg N.day(-1).100 g(-1)).