The serum insulin-like growth factor-II/mannose-6-phosphate receptor in normal and diabetic pregnancy.

The extracellular domain of the insulin-like growth factor-II/mannose-6-phosphate (IGF-II/Man-6-P) receptor is present in the circulation of several species including man. The purpose of the present study was to establish whether this truncated receptor is present in higher concentrations in fetal sera compared with adult sera and whether the metabolic status of the individual alters serum concentrations of this protein. Nondiabetic and diabetic pregnant women were studied throughout gestation, and at term fetal cord sera were obtained. Levels of IGF-I increased throughout pregnancy in normal and diabetic women. IGF-II levels significantly increased during the third trimester in both groups and levels of IGF-I and IGF-II were significantly elevated in fetal cord samples from diabetic women only. Serum samples were gel-filtered on Sephadex G-200, and column fractions were assayed for binding of radiolabeled IGF-II and IGF-I. There was specific binding (SB) of IGF-II in the void volume fractions in all samples examined. Normal women had 3% +/- 0.5% SB, whereas in cord sera SB was 5% +/- 0.7% and in pregnant sera 10% +/- 2%. There was no difference in SB in fetal cord or pregnant samples from normal and diabetic women. In addition, there was a peak of binding activity of both IGF-I and -II in gamma-globulin and postalbumin fractions of the columns in pregnant and nonpregnant women, but only in postalbumin fractions in fetal cord samples.(ABSTRACT TRUNCATED AT 250 WORDS)