Hairloss Study Abstract: Ketoconazole binds to the human androgen receptor.
Title
Ketoconazole binds to the human androgen receptor.
Author
Eil C
Address
Department of Internal Medicine, Naval Hospital, Bethesda, Maryland.
Source
Horm Metab Res, 24: 8, 1992 Aug, 367-70
Abstract
Ketoconazole, an imidazole anti-fungal agent, has often produced features of androgen
deficiency including decreased libido, gynecomastia, impotence, oligospermia, and
decreased testosterone levels, in men being treated for chronic mycotic infections. Based
on these potent effects on gonadal function in vivo as well as previous work in vitro
demonstrating affinity of ketoconazole for receptor proteins for glucocorticoids and
1,25(OH)2 vitamin D3 and for sex steroid binding globulin (SSBG), the binding of
ketoconazole to human androgen receptors (AR) in vitro was also examined. Ketoconazole
competition with [3H]methyltrienolone (R1881) for androgen binding sites in dispersed,
intact cultured human skin fibroblasts was determined at 22 degrees C. Fifty percent
displacement of [3H]R1881 binding to AR was achieved by 6.4 +/- 1.8 (SE) x 10(-5) M
ketoconazole. Additional binding studies performed with ketoconazole in the presence of
increasing amounts of [3H]R1881 showed that the interaction of ketoconazole with AR was
competitive when the data were analyzed by the Scatchard method. It should be noted,
however, that the dose of ketoconazole required for 50% occupancy of the androgen receptor
is not likely to be achieved in vivo, at least in plasma. Finally, androgen binding
studies performed with other imidazoles, such as clotrimazole, miconazole, and
fluconozole, revealed that in this class of compounds only ketoconazole appears to
interact with the androgen receptor. Ketoconazole appears to be the first example of a
non-steroidal compound which binds competitively to both SSBG and multiple steroid hormone
receptors, suggesting that the ligand binding sites of these proteins share some features
in common.