The Evaluation of Androgen Circulating Levels Following Castration in Adult Male Rats

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Abstract
In the present study dehydroepiandrosterone (DHEA), androstenedione (A), testosterone (T) and dihydrotestosterone (DHT) plasma levels were determined in adult male rats five days, seven weeks and eleven weeks after orchiectomy and confronted, respectively, with rats 60 days old which were sacrificed 5 days, 7 weeks and 11 weeks after the sham-operation for orchiectomy. It was revealed that five days after castration A, T and DHT were decreased with respect to sham-operated rats. Seven and eleven weeks after orchiectomy only T remained lower. In all three groups of castrated animals the A/T ratio resulted augmented whereas T/DHT ratio resulted lower with respect to the sham-operated animals. Five days after castration DHEA plasma concentration was positively correlated to A levels and both androgens resulted negatively correlated to T plasma levels. Seven weeks after bilateral orchiectomy an inverse correlation appeared between DHEA/A ratio and T. This emphasizes the role of DHEA and A in maintaining testosterone circulating levels. Seven and eleven weeks following castration the A/T ratio was negatively related to the T/DHT ratio, indicating that A contributes to DHT plasma levels. In the second part of our study the effect of sex steroid administration was evaluated 7 weeks after castration. A linear correlation between DHEA and T circulating levels was obtained following the administration of T while treatment with oestradiol caused a significant increase of the DHEA/A ratio. The castrated animals that received DHT presented lower T circulating levels while the A/T ratio was significantly increased. On the basis of these results, the authors suggest that following castration some adrenal androgen precursors (DHEA and A) are responsible for the maintenance of T and DHT circulating levels. Furthermore, sex steroid administration appears to modulate adrenal androgen circulating levels.