Evidence ia provided for the impermeability of the human placenta for bovine insulin at term. Women in labor received glucose infulions with and without insulin added; the dosage was 1 g glucose and 0.33 units insulin per min. The insulin in cord blood was nearly always elevated after maternal infusions compared with controls, but no difference in fetal insulin concentrations were observed whether insulin was added to mother's infusion or not. Even an 18-fold increase of the maternal insulin level did not affect the insulin level in cord blood. The additional glucose transferred to the fetus by maternal infusion stimulates the fetal insulin secretion with a delay of at least 22 rnin. Harm. Metab. Res. I: 274-275 (1969) K e y -W 0 r d s: Insulin -HUmJln Placenta -Glucose InfUsion, -Fetal Insulin -Insulin StimulationGitlin, Kumate and Morales (1965) have reported that mammalian insulin can pass the placental barrier in human graviditas. In contrast to their results we present evidence that the human placenta is impermeable to insulin during labor period.Patients and Methods lhirteen women in labor received an Lv. infusion of 1 g glucose plus 0.33 units bovine insulin (Altinsulin Hoechst) per min; twelve other women in labor received only glucose (1 g per min), that is 12 to 16 mg glucose per kg body weight per min. The duration of the infusion varied between 18 and 100 min, averaging 48.5 min in group I (glucose plus insulin) and 42.2 in group 11 (glucose only). Eleven women who received no infusion and their offsprings served as controls. Both glucose and insulin were measured in maternal blood at the beginning of the infusion and immediately before the infant was delivered.• This investigation was supported by grants from the "Deutsche Forschungl-Gemeinschaft" and the "Alexander von Humboldt-Stiftung". -A more detailed presentation will appear in J. Obstet. Gynaecol. Brit. Comm. Furthermore, insulin was determined in arterial and venous cord blood. Insulin plasma levels were measured by the radioimmunologic procedure according to Melani, Ditschuneit, Bartelt, Friedrich and Pfeiffer (1965), and blood glucose by the method of Huggett and Nixon (1957). ResultsThe maternal blood glucose level increased in good correlation with the duration of glucose infusion (group I: r = 0.795; group 11: r = 0.783), and so does the glucose in cord blood (vena umbil., group I: r = 0.798, group 11: r = 0.829; arteria umbil., group I: r = 0.774, group 11: r = 0.854). As shown in Tab. 1 plasma insulin level in the parturients tripies du ring the glucose infusion. This increase was correlated with the starting plasma insulin level (r = 0.786), but not with the duration of glucose infusion (r = 0.376). In contrast, the insulin levels in both umbilical vein (Fig. 1) and artery were weil correlated with the duration of infusion (group I: r = 0.835; group 11: r = 0.670, calculated from combined values of arterial and venous cord blood). Extrapolating the duration of infusion to 60 min for better comparison the mean (± S.E.) insulin level in...
Insulin and glucose levels were measured in eleven women in labour and in the umbilical arterial and venous blood of their babies. Twelve women received an infusion of 10 per cent glucose at a rate of 1 g. per minute for an average of 42.2 minutes. Thirteen women were given a similar infusion, and crystalline zinc insulin was added in a concentration of 1 unit to 3 g. of glucose. The average infusion time was 48 -5 minutes.Exogenous insulin did not improve the transplacental passage of glucose. The infusion of glucose with insulin caused an eighteenfold increase in insulin level of the women in labour. This change was not reflected by the levels of insulin in umbilical blood. Similar umbilical insulin levels after both types of infusion show that exogenous insulin does not pass from the mother to the fetus during labour. An increase in the insulin level of umbilical blood began 22 minutes after the start of the infusion. This most probably reflects the poor capacity of the fetal pancreas to react to changes in blood glucose levels. 121
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