It is known that both catecholamines (CA) and cortisol (F) levels elevate during labor. To determine the correlation between adrenal steroids and medullary function, maternal blood was collected during pregnancy, first stage of labor (MVI) and at delivery (MVII). Umbilical arterial and venous blood (UA, UV) was also obtained at delivery. Further, ACTH or dexamethasone (Dx) was given during the first stage of labor, and maternal blood was collected before and 30 minutes after the administration. Plasma levels of CA [noradrenaline (NA), adrenaline (Ad)] were extracted by trihydroxyindole method and were measured by HPLC. DHA-S and F levels were determined by specific RIA.
Results are as follows :
1. No apparent change was observed in maternal NA and Ad levels throughout pregnancy. DHA-S levels were high in first trimester and decreased as pregnancy advanced, while F levels showed an increase trend as pregnancy progressed.
2. All hormone levels in maternal blood increased remarkably during labor. A significant negative correlation between F and Ad levels at delivery was noted. When F levels were elevated by ACTH administration, Ad levels decreased. Ad levels elevated when F levels were suppressed by Dx administration.
3. NA, Ad and DHA-S levels in cord blood were higher than those in MVII. Levels of F in maternal blood were higher than those in cord blood. A significant correlation of F in MVII and UA was observed. These results indicate that the suppressive effect of F may be involved in the mechanism of Ad secretion, though the secretion of Ad increased with F in the course of labor. The response of fetal adrenal to the stress of labor may be different from that of maternal adrenal since a significant correlation was not noticed between the levels of Ad and cortisol in cord blood as was found in maternal blood.
