Plasma immunoreactive endothelin-1 concentration in human fetal blood: its relation to asphyxia.

To elucidate the effects of birth stress on immunoreactive endothelin-1 (irET-1) concentrations in fetal blood, we determined irET-1 levels in cord plasma in different modes of delivery associated with or without complications such as asphyxia. The irET-1 concentrations in both the umbilical artery and vein were significantly higher than those found in maternal venous blood at delivery, although there was no significant difference between preterm and full-term infants. When plasma irET-1 concentrations of healthy infants born by vaginal delivery and by cesarean section without labor were compared, the former had significantly (p less than 0.05) higher levels than the latter (15.4 +/- 4.9 pg/mL versus 11.1 +/- 3.1 pg/mL). Furthermore, umbilical venous plasma obtained from vaginally delivered infants complicated by asphyxia showed significantly (p less than 0.001) higher irET-1 levels (28.2 +/- 9.4 pg/mL) than those of nonasphyxiated infants (14.2 +/- 4.5 pg/m). These data suggest that birth stress, especially asphyxia, may contribute to the increase in fetal circulating irET-1 levels.

Thyroid-stimulating activity of human chorionic gonadotropin in sera of normal pregnant women.

To ascertain the thyrotropic activity of human chorionic gonadotropin in sera of normal pregnant women, we examined the adenylate cyclase activation in the cultured FRTL-5 cells by extracted hCG from 7 normal pregnant women. hCG was extracted from the sera using anti-hCG-beta subunit monoclonal antibody-coated microwells, eluted with 2 mol/l guanidine-HCl, and reconstituted with hypotonic Hanks' solution. FRTL-5 cells were precultured in 5H medium, incubated for 2 h with the serum extracts, and the cAMP released into the medium was measured. hCG levels in serum extracts ranged from 1100 to 6800 IU/l; values corresponded to 1.4-19.8% compared with those in the original serum samples. Addition of the extracts to FRTL-5 cells resulted in significant increases in the cAMP accumulation, ranging from 9.8 to 59.0 nmol/l. cAMP levels were also increased in a dose-dependent manner by adding purified hCG as well as crude hCG and hTSH to FRTL-5 cells. These findings suggest that the thyroid gland of normal pregnant women may actually be stimulated by hCG itself.

Thyroid-stimulating activity in sera of normal pregnant women.

To evaluate the effect of a thyroid stimulator on thyroid function in the sera of normal pregnant women, we measured thyroid-stimulating activity (TSA) using a highly sensitive bioassay based on cAMP accumulation in cultured rat FRTL-5 thyroid cells. Serum was pretreated with 10% polyethylene glycol (PEG), and the supernatant (PEG-pretreated serum) was then used in the following studies. FRTL-5 cells were preincubated in 5H medium and incubated for 2 h with PEG pretreated serum, and cAMP was measured. All 11 patients with untreated hyperthyroid Graves' disease with strongly positive thyroid-stimulating antibody activity had normal TSA, because only 5.6% of their immunoglobulin G was recovered in the PEG-pretreated serum. In 32 normal pregnant women, 29 (91%) had positive TSA. Their TSA showed statistically significant positive correlations with serum hCG and free T4 levels, and a negative correlation with serum TSH levels. Moreover, when hCG was absorbed from sera by incubation with the solid phase anti-HCG monoclonal antibody, a significant positive correlation was observed between the rate of decrease in hCG and that in TSA. In conclusion, 1) TSA exists in the sera of normal pregnant women, which reflects hCG itself; and 2) thyroid glands of normal pregnant women may be stimulated by TSA to induce a slight suppression of TSH but not sufficient to induce overt hyperthyroidism.