Role of hypothalamic-pituitary axis in EGF action on maturation of adrenal gland in fetal rhesus monkey in vivo

Abstract

We determined the route of action of epidermal growth factor (EGF) [intraperitoneal (IP) versus intraamniotic administration] on adrenal development and whether its effects are mediated via the fetal hypothalamic-pituitary axis in the fetal rhesus monkey in vivo. EGF (40 μg) was administered IP (n = 9) or intraamniotic (n = 6) at 121, 123, 125, and 127 d gestation (term, approximately 165 ± 10 d gestation). In addition, a competitive corticotropin-releasing factor antagonist ([D-phenylalanine12, Norleucine21.38] corticotropin-releasing factor12-41 to block fetal pituitary ACTH secretion; 400 μg IP) and metyrapone (11β-hydroxylase inhibitor to block adrenal cortisol synthesis; 15 mg IP and 15 mg intraamniotic) were administered, in combination with EGF (EGF+BLOCK; 40 μg IP; n = 4 fetuses). Control fetuses (n = 6) received saline injections in an equivalent volume. On gestational d 128, a hysterotomy was performed, and fetal adrenals were collected for morphometric analyses and immunocytochemical localization of 3β-hydroxysteroid dehydrogenase (3βHSD) and cytochrome P-450 11β-hydroxylase/aldosynthase. Definitive zone (DZ) width and cortical width of 3βHSD staining were significantly greater (p < 0.05) in the EGF IP-treated fetuses compared with controls and EGF+BLOCK. With EGF IP, >HSD was increased in the DZ and induced extensively in the transitional zone of the fetal adrenal cortex, and cytochrome P-450 11β-hydroxylase/aldosynthase immunoreactivity was induced to detectable levels in the DZ. The administration of EGF+BLOCK inhibited the expression of 3βHSD in the transitional zone, but βHSD expression was still increased in the DZ and cytochrome P-450 11β-hydroxylase/aldosynthase immunoreactivity was induced in the DZ. EGF intraamniotic administration had no significant effect on the width of the DZ or cortical width of 3βHSD staining compared with controls. These data suggest that EGF acts via the hypothalamic-pituitary axis to modulate adrenal cortical growth and functional maturation of the transitional zone (the putative zona fasciculata), whereas EGF can act independently of the hypothalamic-pituitary axis to stimulate functional maturation of the DZ (the putative zona glomerulosa).