Triiodothyronine and Estradiol Increase the Serum Level of Androstanediol Glucuronide but Do Not Influence Androgen UDP-Glucuronyl Transferase Activity in the Female Rat

Summary

In this study, adult female rats were treated with either estradiol, testosterone or triiodothyronine (T₃). The mean ± SD for serum levels of androstane-3α,17β-diol glucuronide (ADIOL-G) in rats injected with estradiol (31.1 ± 6.1 nmol/l) and T₃ (28.7 ± 6.1 nmol/l) increased three-fold in comparison to the controls (9.2 ± 3.6 nmol/l; p<0.01). There was no significant increase in ADIOL-G levels in rats injected with testosterone (12.0 ± 3.4 nmol/l) even though serum testosterone levels increased more than 17-fold (1.2 ± 0.3 nmol/l; p < 0.01). Testosterone levels remained below the detection level of the assay (0.07 nmol/l) in the control and the estradiol and T₃ treattment groups. Androgen UDPGT activity in liver microsomes was not altered by treatment with testosterone, estradiol or T₃. However, the UDPGT activity for p-nitrophenol increased two-fold in estradiol and T₃-treated females (p<0.01), but was not significantly altered by testosterone treatment. These results suggest that the activity of androgen UDPGT in liver is not the limiting factor in the increased serum levels of ADIOL-G observed on treatment with estradiol and T₃.

Key words

Androgen Metabolism - Androstanediol Glucuronide - Triiodothyronine - Estradiol - Testosterone - Androgen Glucuronyl Transferase