Late pregnancy maternal and fetal time-course of plasma ACTH and corticosterone after continuous ether inhalation by pregnant rats. Cytoimmunological study of fetal hypophyseal cells.

In order to compare the time-course and the amplitude of the hypophyseal-adrenal response to stress in both the mother and the fetus, female rats on day 20 of pregnancy were subjected to continuous ether inhalation and killed at different time intervals after the onset of stress (5, 10, 20, 30, 40 and 60 min). Plasma ACTH was determined by radioimmunoassay and plasma corticosterone by a competitive binding radioassay. In normal pregnant rats subjected to ether stress, the release of ACTH is tenfold higher than in the fetus, but the amplitude of maternal and fetal corticosterone release after this stimulus is very similar; the response occurs faster in the mother than in the fetus. In pregnant rats adrenalectomized 4 h before ether stress procedure, the ACTH release is smaller than in normal mothers and the plasma corticosterone values, despite the adrenalectomy, are close to those observed in resting rats at the same time of day. The fetal corticosterone release is still elevated under this stimulus and occurs faster than in fetuses from normal mothers. The cytoimmunological study of fetal hypophysis revealed both hypertrophy and hyperplasy of ACTH-containing cells during the first minutes of ether anesthesia.