The effect of chronic hyperinsulinemia on ovine fetal growth

Infusion of exogenous insulin for 18 days to seven ovine twin fetuses caused hyperinsulinemia (31.0 +/- 6.9 microU/ml) when each was compared to its sham-infused twin (6.6 +/- 0.7 microU/ml). The hyperinsulinemic fetuses also had lower arterial serum glucose concentrations (0.77 +/- 0.07 mM) than their sham-infused controls (1.10 +/- 0.04 mM). There were no significant changes in fetal weight or height attributable to insulin infusion. Our methods would have detected a 12% difference in fetal weight; therefore, the lack of effect of insulin on fetal weights was not due to excessive variability of the difference in weights between twins. Hyperinsulinemia increased the myocardial cellular contents of protein and RNA, which suggested that myocardial hypertrophy occurred; however, heart weight itself was not significantly increased. This apparent contradiction may be due to considerable variability in heart weight. From the above data, we conclude that 19 days of documented ovine fetal hyperinsulinemia does not increase the growth rate of the nearterm ovine fetus.