Lok F, Owens J A, Mundy L, Robinson J S, Owens P C
Department of Obstetrics and Gynaecology, University of Adelaide, Australia.
Am J Physiol. 1996 May;270(5 Pt 2):R1148-55. doi: 10.1152/ajpregu.1996.270.5.R1148.
Insulin-like growth factor I (IGF-I) is required for normal fetal growth and skeletal maturation in late gestation, because null mutations of the IGF-I gene in mice reduce fetal weight and retard ossification of bones. To determine if, conversely, increased abundance of IGF-I promotes fetal growth and skeletal maturation, fetal sheep were infused intravascularly with recombinant human IGF-I (n = 7) (26 +/- 3 micrograms. h-1.kg-1) from 120 to 130 days gestation and compared with controls (n = 15). IGF-I infusion increased plasma IGF-I concentrations by 140% (P = 0.002) and weights of fetal liver, lungs, heart, kidneys, spleen, pituitary, and adrenal glands by 16-50% (P < 0.05). Weights and/or lengths of the fetus, placenta, gastrointestinal tract, individual skeletal muscles, and long bones were unchanged by IGF-I. However, IGF-I increased the percentage of proximal epiphyses of long bones present (P < 0.05) and their cross-sectional areas by 15 to 38% (P < 0.05). These results show that IGF-I promotes growth of major fetal organs, endocrine glands, and skeletal maturation in vivo, consistent with IGF-I actively controlling and not merely facilitating fetal growth. The variable response of different tissues may partly reflect tissue specificity in growth requirements for additional factors.
胰岛素样生长因子I（IGF-I）是妊娠晚期胎儿正常生长和骨骼成熟所必需的，因为小鼠中IGF-I基因的无效突变会降低胎儿体重并延缓骨骼骨化。为了确定相反地，IGF-I丰度增加是否会促进胎儿生长和骨骼成熟，在妊娠120至130天时，给胎羊血管内输注重组人IGF-I（n = 7）（26±3微克·小时-1·千克-1），并与对照组（n = 15）进行比较。输注IGF-I使血浆IGF-I浓度增加了140%（P = 0.002），胎儿肝脏、肺、心脏、肾脏、脾脏、垂体和肾上腺的重量增加了16%至50%（P < 0.05）。胎儿、胎盘、胃肠道、单个骨骼肌和长骨的重量和/或长度未因IGF-I而改变。然而，IGF-I增加了长骨近端骨骺的出现百分比（P < 0.05），其横截面积增加了15%至38%（P < 0.05）。这些结果表明，IGF-I在体内促进主要胎儿器官、内分泌腺的生长和骨骼成熟，这与IGF-I积极控制而非仅仅促进胎儿生长一致。不同组织的可变反应可能部分反映了对其他因素生长需求的组织特异性。
