Developmental changes in rabbit and dog adrenal function: a possible homologue of adrenarche in the dog

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Abstract
Histologic, hormonal, and enzymatic studies were performed in the rabbit and dog to identify maturational changes similar to human adrenarche. Development of an adrenal reticular zone was observed in both the rabbit and dog, analogous to the change in the man. Plasma dehydroepiandrosterone (DHA) and androstenedione (delta 4-A) increased significantly in postpubertal compared to prepubertal male rabbits and dogs, but the increases were much smaller than those reported in man. Orchiectomy reduced plasma DHA and delta 4-A of adult rabbit and dog to near undetectable levels, suggesting a primarily testicular origin. The activities of adrenal microsomal 17-hydroxylase and 17,20-desmolase in the orchiectomized rabbit and dog were subsequently measured to explain this apparent low adrenal contribution to DHA and delta 4-A. Adrenal 17-hydroxylase activity in the rabbit ad 17,20-desmolase activity in both the rabbit and dog were significantly lower than in an adrenal androgen-secreting primate (cynomolgus macaque). Adrenal 17-hydroxylase activity in the dog, measured 1 wk after castration, doubled after sexual maturation (P less than 0.001). This change was paralleled by a significant rise in basal and ACTH-stimulated plasma 17-hydroxyprogesterone in the intact dog (P less than 0.05). Because adrenal 17-hydroxylase activity has been shown to increase during adrenarche in man, this change may be homologous to human adrenarche.