Metabolic effects of IGF-I in the growth retarded fetal sheep.
It has been shown that IGF-I has an anabolic effect in the normal fetus. However, there is evidence to suggest that there may be IGF-I resistance in the growth retarded fetus. Therefore, we investigated the effects of acute IGF-I infusion to chronically catheterised fetal sheep. At 128 days gestation, fetuses underwent a 4 h infusion of IGF-I (50 microg/kg/h). Three groups of animals were studied. Nine normally grown fetuses were studied as controls. Embolised animals (n=8) received microspheres into the uterine vasculature, and animals with spontaneous intra-uterine growth retardation (IUGR animals) (n=6) were fetuses found at post mortem to be spontaneously growth restricted. The effects of IGF-I infusion on feto-placental carbohydrate and protein metabolism were similar in our control group to previous similar experiments. IGF-I infusion decreased fetal blood glucose, oxygen, urea and amino-nitrogen concentrations, and inhibited placental lactate production. The same fetal blood metabolite concentrations also fell during IGF-I infusion in the embolised fetuses, but the effect on placental lactate production was not seen. The only effect of IGF-I infusion in the spontaneous IUGR animals was a fall in fetal blood amino-nitrogen concentrations. We conclude that fetal IGF-I infusion does not have the same anabolic effects in the growth retarded fetus as the normal fetus. In addition, the effects of IGF-I were different in the two growth retarded groups. Our data support previous evidence that the growth retarded fetus has altered IGF-I sensitivity, and this may vary depending on the cause, severity and duration of growth retardation.
Jensen
E C
EC
Research Centre for Developmental Medicine and Biology, School of Medicine, Private Bag 92019, Auckland, New Zealand.
Harding
J E
JE
Bauer
M K
MK
Gluckman
P D
PD
D000818:Animals; D001786:Blood Glucose / Q000032:analysis*; D001806:Blood Urea Nitrogen; D005312:Fetal Blood / Q000737:chemistry*; D005317:Fetal Growth Retardation / Q000196:embryology* / Q000378:metabolism*; D007334:Insulin-Like Growth Factor I / Q000032:analysis / Q000494:pharmacology*; D008954:Models, Biological; D010100:Oxygen / Q000097:blood; D012756:Sheep
D001786:Blood Glucose; D007334:Insulin-Like Growth Factor I; D010100:Oxygen