Insulin effect on fetal glucose utilization.

Insulin infused into a sheep fetus over a 3-hr period at the rate of approximately 0.24 U.kg-1.h-1 increased fetal glucose uptake (utilization) from 4.4 +/- 0.7 mg.min-1.kg-1 to 6.9 +/- 0.9 mg.min-1.kg-1 as compared to a noninsulin control period. Insulin administration did not alter fetal oxygen consumption (8.6 +/- 0.7 ml.min-1.kg-1 vs. 7.7 +/- 0.7 ml.min-1.kg-1), umbilical blood flow (220 +/- 1 ml.min-1.kg-1 vs. 209 +/- 16 ml.min-1.kg-1), or the placental clearances of antipyrine (114 +/- 7 ml.min-1.kg-1 vs. 109 +/- 8ml.min-1.kg-1) and urea (24.5 +/- 2.2 ml.min-1.kg-1 vs. 25.0 +/- 2.1 ml.min-1.kg-1). Fetal plasma glucose concentration fell significantly (0.22 +/- 0.01 mg.ml-1 to 0.16 +/- 0.01 mg.ml-1) during insulin infusion. The insulin effect on fetal glucose uptake occurred over a range of maternal glucose concentrations (0.32 leads to 0.78 mg.ml-1), which were not altered by the infusion of insulin in the fetal compartment. Insulin has a specific effect on increasing fetal glucose uptake and utilization.