Metribolone is a potent, non-aromatizable androgen which has also been used as a photoaffinity label for the androgen receptor. It is the 17-methylated derivative of trenbolone, and is a similarly potent anabolic steroid, but with high hepatotoxicity. The in vitro conversion of the synthetic steroidal androgen methyltrienolone (17 beta-hydroxy-17 alpha- methylestra -4,9,11-trien-3-one) to an estrogen was investigated. Methyltrienolone did not compete with testosterone in this very active aromatase system, nor did it inhibit the aromatization. While the placental aromatase very efficiently converted testosterone to estrogens, it did not convert methyltrienolone [3H] to estrogenic (phenolic) products. Homogenates of rat hypothalamic tissue were also unable to aromatize methyltrienolone, although they converted small quantities of testosterone to estradiol and 19-hydroxyandrostenedione to estrone.
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