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Abstract

Trends of reproductive hormones in male rats during psychosocial stress: Role of glucocorticoid metabolism in behavioral dominance (PDF) (HTML) 
Hardy,Matthew P.; Sottas,Chantal M.; Ge,Renshan; McKittrick,Christina R.; Tamashiro,Kellie L.; McEwen,Bruce S.; Haider,Syed G.; Markham,Christopher M.; Blanchard,Robert J.; Blanchard,D.Caroline; Sakai,Randall R.
Biology of Reproduction 67(6): 1750-1755
Publication date: 2002

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Stress in socially subordinate male rats, associated with aggressiveattacks by dominant males, was studied in a group-housing contextcalled the visible burrow system (VBS). It has been establishedthat subordinate males have reduced serum testosterone (T) andhigher corticosterone (CORT) relative to dominant and singlyhoused control males. The relationship of the decreased circulatingT levels in subordinate males to changes in serum LH concentrationshas not been evaluated previously. Since decreases in LH duringstress may cause reductions in Leydig cell steroidogenic activity,the present study defined the temporal profiles of serum LH,T, and CORT in dominant and subordinate males on Days 4, 7,and 14 of a 14-day housing period in the VBS. The same parameterswere followed in serum samples from single-housed control males.Leydig cells express glucocorticoid receptors and may also betargeted for direct inhibition of steroidogenesis by glucocorticoid.We hypothesize that Leydig cells are protected from inhibitionby CORT at basal concentrations through oxidative inactivationof glucocorticoid by 11ß-hydroxysteroid dehydrogenase(11ßHSD). However, Leydig cell steroidogenesis isinhibited when 11ßHSD metabolizing capacity is exceeded.Therefore, 11ßHSD enzyme activity levels were measuredin Leydig cells of VBS-housed males at the same time points.Significant increases in LH and T relative to control were observedin the dominant animals on Day 4, which were associated withthe overt establishment of behavioral dominance as evidencedby victorious agonistic encounters. Serum LH and T were lowerin subordinate males on Day 7, but T alone was lower on Day14, suggesting that lowered LH secretion in subordinates maygradually be reversed by declines in androgen-negative feedback.Serum CORT levels were higher in subordinate males comparedto control at all three time points. In contrast, oxidative11ßHSD activity in Leydig cells of dominant maleswas higher relative to control and unchanged in subordinates.These results suggest the following: 1) failure of Leydig cellsof subordinate males to compensate for increased glucocorticoidaction during stress, by increasing 11ßHSD oxidativeactivity, potentiates stress-mediated reductions in T secretion;and 2) an inhibition of the reproductive axis in subordinatemales at the level of the pituitary.

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