Disappearance of labelled IGF-2 from plasma of the ovine fetus in late gestation.
The role of IGF-2 in the fetus and its possible influence on fetal growth remains speculative. We investigated the size distribution of unsaturated binding sites for labelled oIGF-2 in ovine fetal plasma. In addition, the disappearance of each form of protein bound IGF-2 in the late gestation ovine fetus (125-135 days, n = 5) was estimated. One minute after injection into the fetal femoral vein, 125IoIGF- circulated in the fetal femoral artery bound primarily to a 50 kDa binding protein. Only a small amount of binding to a 150 kDa binding protein was seen with little to no free IGF-2 present. IGF-2 also circulated in association with a large molecular weight complex (ca. 250 kDa) presumed to be circulating receptor bound IGF-2. The half life of the 250 kDa form of IGF-2 was 385.9 +/- 65.4 min, for the 150 kDa form 308.0 +/- 65.0 min, for the 50 kDa form was 35.5 + 2.6 min and for the free form of IGF-2 was 1.6 +/- 0.6 min. There was no apparent movement of intact IGF-2 out of the fetal circulation into any of the fetal fluids or into the maternal circulation. Similarly there was no consistent placental uptake of IGF-2 from the fetal circulation.
Bassett
N S
NS
Department of Paediatrics, University of Auckland, New Zealand.
Breier
B H
BH
Moore
L
L
Gluckman
P D
PD
D000818:Animals; D001665:Binding Sites; D001798:Blood Proteins / Q000378:metabolism; D002352:Carrier Proteins / Q000378:metabolism; D005260:Female; D005312:Fetal Blood / Q000378:metabolism*; D005865:Gestational Age; D006207:Half-Life; D018969:Insulin-Like Growth Factor Binding Proteins; D007335:Insulin-Like Growth Factor II / Q000493:pharmacokinetics*; D010920:Placenta / Q000378:metabolism; D011247:Pregnancy; D011485:Protein Binding; D012756:Sheep
D001798:Blood Proteins; D002352:Carrier Proteins; D018969:Insulin-Like Growth Factor Binding Proteins; D007335:Insulin-Like Growth Factor II