Binding of 7α,17α-Dimethyl-19-Nortestosterone (Mibolerone) to Androgen and Progesterone Receptors in Human and Animal Tissues*

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Abstract
In rat uterus and prostate, 7α,17α-dimethyl-19-nortestosterone (DMNT) binds to the androgen receptor specifically and with high affinity. However, this steroid does not bind to glucocorticoid receptors, since it does not displace binding of [3H]triamcinolone acetonide in calf thymus cytosol. In calf uterine and human breast tumor cytosols DMNT binds to the androgen and progesterone receptors, since binding of [3H] DMNT is displaced by unlabeled 16α-ethyl-21-hydroxy-19-nor-4-pregnene-3,20-dione triamcinolone acetonide, and 5a-dihydrotestosterone (DHT). Conversely, binding of [3H]16α-ethyl-21- hydroxy-19-nor-4-pregnene-3,20-dione is effectively competed for by unlabeled DMNT but not by DHT. The observed differences in binding of [3H]DMNT to rat and calf uterine cytosols suggest the species specificity of progesterone receptors. Unlike DHT, DMNT has no appreciable binding to human sex-steroid binding globulin. These findings suggest DMNT as a suitable ligand for measurement and characterization of androgen receptors in rat and human prostate. (Endocrinology118: 1327-1333, 1986)