The effects of dexamethasone treatment of pregnant rats on maternal, fetaland neonatal ACTH-cells

Adrenocorticotropic hormone (ACTH) is secreted in response to a number of s timuli and if influences growth, differentiation and adrenal steroidogenesi s. Rat pituitary ACTH-cells are differentiated at 14-16 days of fetal life, while synthesis of adrenal glucocorticoids starts from the 17th day of ges tation as a result of increased synthesis and release of ACTH. The aim of t his work was to examine the effect of dexamethasone (Dx), administered to g ravid females, on the synthetic ability of their pituitary ACTH-cells as we ll as those of their fetal and neonatal offspring. The experimental group o f pregnant females received Dr (1.5 mg/kg bw) on day 16 of gestation, while the control group received an equal volume of diluent at the same time. Pl asma ACTH and cortisol concentrations were determined by RIA. The ACTH-cell s were examined under light and electron microscopes. The results obtained indicate that single Dr-treatment of pregnant rats sup presses differentiation of fetal adrenocortical cells and the release of AC TH. However, in neonatal rats the number of ACTH- and precursor cells and t heir proliferation increased, as well as ACTH and cortisol synthesis and re lease, i. e. stimulation of synthesis and secretion of ACTH was noticed aft er suppression in the fetal period. The numerous changes observed in the fetuses and early neonates of dams tre ated with a single dose of Dr during pregnancy had disappeared in 30-day-ol d offspring.