Effect of Streptozotocin on Foetal Lambs in Mid-pregnancy

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Abstract
Streptozotocin was administered to 11 fetal lambs in utero at 70-85 days of gestation. Four of the fetuses survived and, when delivered at 134-142 days, exhibited significant growth retardation of the trunk and delayed osseous maturation in limb bones. The fetal kidneys and livers were most affected, but in 3 of the 4 fetuses, the weight of the brain was appropriate for gestational age. Head size, measured by length or biparietal diameter, was normal. The insulin content of the fetal pancreas was less after streptozotocin-treatment than in normal animals of a similar gestation. Two streptozotocin-treated fetuses, catheterized at 120 days gestation, had higher glucose concentrations and lower insulin responses than controls when infused with glucose. Plasma concentrations of ovine placental lactogen were lower in streptozotocin-treated fetuses than in controls, but serum somatomedin-like activity measured by receptor assay was greater than in controls. When the fetal serum was chromatographed on Sephadex G150 at acid pH, the major increase in somatomedin-like activity was found in the smaller MW fraction (MW .apprx. 10,000). The fetal growth retardation associated with streptozotocin administration in midpregnancy may be due to insulin deficiency, but the normal brain weight which occurred suggests that some other factor (possibly a somatomedin) regulates the growth of this organ.