Free and bound insulin in pregnancy and labor

Summary

The plasma insulin was fractionated on strong sulfocationites: IR-120 in sodium form and SDV-3 in hydrogen form; the insulin bio-assay was carried out according to the glucose uptake of rat epididymal fat pad. The results were expressed as extra glucose uptake, in mg/g/3 h. In 12 nonpregnant fasting females of child-bearing age the activity of free insulin was 1.391±0.282 and that of bound insulin-3, 162±2.267 mg/g/3 h. In 18 women at 24–36 weeks of pregnancy the values were 2.724±0.410 and 2.983±0.342 mg/g/3h respectively. At the time of delivery in 12 women the content of free insulin in maternal venous blood was 9.948±0.313 and that of bound insulin-1.434±0.352; in the blood of umbilical vein the values were 2.030±0.470 and 2.597±0.476 mg/g/3 h respectively. The increased level of free insulin in pregnancy is significant (P<0.02). There was a positive correlation of bound insulin in pregnancy is significant (p<0.02). There was a positive correlation of bound insulin levels in maternal and fetal blood (r=0.440; p=0.05) and a negative and not significant correlation of free insulin levels (r=0.404; P>0.05). The latter fact points to the insulin impermeability of placenta.