Androgen Binding Profiles of Two Distinct Nuclear Androgen Receptors in Atlantic Croaker (Micropogonias Undulatus)

The study conducted 23 years ago investigated the binding affinities of 28 androgens for two nuclear androgen receptors, AR1 and AR2, in Atlantic croaker's brain and ovarian tissues. The researchers discovered that 5α-reduction of steroids generally increased the metabolite's binding affinity for AR2 while decreasing it for AR1. Few androgens bound to AR1 with high affinity, and modifications to the basic structure of testosterone usually reduced its binding affinity for AR1. However, androgens with ketone groups at the 3- and 17-position bound with high affinity to AR1, provided that the androgen had either a 5α-reduced A-ring or a third ketone group at the 11-position. The binding of androgens to AR2 showed a more predictable pattern, with 5α-reduced steroids binding better than 4-ene steroids. AR2 has a broader affinity for androgens and a greater affinity than AR1 for structurally diverse androgens. The different androgen binding affinities of AR1 and AR2 suggest that these two nuclear androgen receptors may mediate the physiological actions of different androgens in teleosts.