Androgen receptor-mediated regulation of adrenocortical activity in the sand rat, Psammomys obesus
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The wild sand rat, Psammomys obesus, displays seasonal variations in adrenocortical activity that parallel those of testicular activity, indicating functional cross-talk between the hypothalamo-pituitary-adrenal and hypothalamo-pituitary–gonadal axes. In the present study, we examined androgen receptor (AR)-mediated actions of testicular steroids in the regulation of adrenocortical function in the sand rat. Specifically, we examined the expression of AR in the adrenal cortex, as well as adrenal apoptosis in male sand rats that had been surgically castrated or castrated and supplemented with testosterone; biochemical indices of adrenocortical function and hormone profiles were also measured. Orchiectomy was followed by an increase in adrenocorticotropic hormone secretion from the anterior pituitary and subsequently, increased adrenocortical activity; the latter was evidenced by orchiectomy-induced increases in the adrenal content of cholesterol and lipids as well as adrenal hypertrophy (seen as an elevation of the RNA/DNA ratio). Further, androgen deprivation respectively up- and downregulated the incidence of apoptosis within the glucocorticoid-producing zona fasciculata and sex steroid-producing zona reticularis. Interestingly, orchiectomy resulted in increased expression of AR in the zona fasciculata. All of the orchiectomy-induced cellular and biochemical responses were reversible after testosterone substitution therapy. Together, these data suggest that adrenocortical activity in the sand rat is seasonally modulated by testicular androgens that act through AR located in the adrenal cortex itself.
KeywordsAndrogen receptor Adrenal cortex Testosterone Apoptosis Sand rat
The authors thank all the personnel of Beni-Abbes Station in the Algerian Sahara for trapping the sand rats used in this study. They also thank M.T. Laurent, N. Mouterfi, and R. Stoffel for technical assistance. The support of the Algerian Ministry of Higher Education and Scientific Research, the Max Planck Institute of Psychiatry (Munich, Germany), the Life and Health Sciences Research Institute (ICVS) of the University of Minho (Braga, Portugal) and the Université Catholique de Lyon (France) is acknowledged. Support from the Algerian–French collaborative Project 09 MDU 756 is also acknowledged.
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