Abstract
While insulin is a critical growth stimulating hormone during the newborn period, other factors as litter size affect fetal growth. We compared the effect of insulin alone versus reducing litter size upon growth. In one model of macrosomia, we injected fetal rats in situ with insulin (I) or saline (S) on day 18 of gestation (term 21.5). In the other, we reduced fetal number by selectively ligating (L) arteries in the secondary cascade of uterine vessels on day 15, Fetuses of sham operated mothers were controls (C). L reduced litter size to 5±2 fetuses, while C, I, and S averaged 8-10 fetuses. Newborn I pups weighed 5,21±.05g (C 5.01±.09g). I and L pups developed hypoglycemia to the same extent compared to their controls but at different points during the newborn period: I pups at 120 and 240 min (30.0±.3 v 45.9±5.7 mg/dl, p .01). L pups at 0, 20, and 60 min (73.2±2.6 v 91.0±4.9 mg/dl, p .01). At these times, I and L pups were hyperinsulinemic compared to their controls (I 46.8±9.6 v S 22.7±3.7 uU/ml, p .01; L 111.0±20.2 v C 52.5±12.0 uU/ml, p 01). Plasma glucagon did not differ between I and L and their controls during fetal and neonatal life (485.6 860.0 pg/ml). I and L pups had significantly elevated hepatic glycogen at birth and 20 minutes. Providing excess insulin without extra metabolic fuels can enhance fetal growth. Limiting litter size also accelerates fetal growth. The surprising finding of hyperinsulinemia and neonatal hypoglycemia in L suggesting that limiting, litter size may enhance fuel provision to the remaining fetuses.
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Finley, S., Ogata, E. EXOGENOUS INSULIN AND FETAL ABLATION: MECHANISMS FOR 2 MODELS OF FETAL MACROSOMIA IN THE RAT. Pediatr Res 21 (Suppl 4), 212 (1987). https://doi.org/10.1203/00006450-198704010-00276
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DOI: https://doi.org/10.1203/00006450-198704010-00276