Adrenarche in the rat

Abstract

Normal pubertal development in humans involves two distinct processes: maturation of adrenal androgen secretion (adrenarche) and activation of the hypothalamic-pituitary-gonadal axis (gonadarche). One factor thought to contribute to the adrenarche in man is increased adrenal 17-hydroxylase (CYP17) activity. In the rat, there is evidence for adrenal involvement in the initiation of puberty, but the adrenal glands of this species are generally thought to express CYP17 only very poorly at best. To further examine the nature of postnatal adrenal development in rat, plasma samples and adrenal tissues were taken from animals aged 2-90 days, circulating adrenal steroids assayed, and adrenal zones assessed quantitatively. A relative increase in zona reticularis, and peaks of circulating cortisol, androstenedione, and 17-OH-progesterone were observed around postnatal days 16-20, clearly before the development of the gonads, which begins at 30-35 days. Quantitative reverse transcriptase PCR confirmed a peak in mRNA coding for CYP17 in adrenal tissue from rats of similar age. The results suggest that the rat adrenal has the capacity to secrete steroids arising from 17-hydroxylation, and that this may contribute to a process similar to human adrenarche.

The transformation of hormonal stress responses throughout puberty and adolescence

“…Indeed, our data show that following stress exposure, prepubertal animals have a higher adrenal corticosterone concentration than mid-pubertal and adult animals, and thus, the extended stress-induced corticosterone response prior to puberty may be related to this difference. Despite the fact that our adrenal homogenates contain the adrenal cortex and the medulla, the size of the adrenal cortex significantly increases in a fairly linear fashion between 30 and 70 days of age (Pignatelli et al 2006), suggesting that our adrenal corticosterone data are not just an artifact of the corticosterone being diluted by growth restricted to the medulla. Regardless, future studies will need to assess changes in steroidogenic enzymes responsible for the production of corticosterone in the adrenal cortex, such as 11b-hydroxylase (Mellon et al 1995, Engeland et al 1997, as our data suggest, there may be a pubertal decline in these enzymes.…”

Developmental programming of adult adrenal structure and steroidogenesis: effects of fetal glucocorticoid excess and postnatal dietary omega-3 fatty acids

“…Exposure to dexamethasone prenatally had no effect on either total adrenal volume or that of the zona fasciculatareticularis in adult offspring. The fasciculata and reticularis regions were considered as a single zone, because the adult rat does not possess a conventional zona reticularis expressing Cyp17a1 (Pelletier et al 2001, Pignatelli et al 2006 and the reticularis cells contribute to corticosterone synthesis (Bell et al 1979). The absence of a programmed increase in adrenal volume or expression of steroidogenic genes indicates that basal adrenal steroidogenesis was not chronically up-regulated in offspring of mothers treated with dexamethasone.…”

“…The zona glomerulosa and adrenal medulla were readily identified morphologically, and the area between these regions was considered as a single zone (zona fasciculatareticularis) because the adult rat does not possess a conventional zona reticularis expressing Cyp17a1 (Pelletier et al 2001, Pignatelli et al 2006. Rather, the reticularis cells are thought to contribute to corticosterone synthesis (Bell et al 1979).…”

Adolescence: A central event in shaping stress reactivity

“…Unlike the dramatic increase in basal gonadal hormone titers during puberty, basal levels of stress hormones remain relatively constant (Pignatelli, Xiao, Gouveia, Ferreria, & Vinson, 2006). For instance, studies that have assessed ACTH and corticosterone concentrations in prepubertal and adult animals typically find that basal levels of these hormones are similar at both ages.…”