Increased androgen binding capacity in sebaceous glands in scalp of male-pattern baldness

Sebaceous glands were isolated by manual dissection under a microscope from surgical specimens of scalp skin with male pattern baldness and skin specimens of hairy and bald scalp obtained at autopsy. The 800 X g pellet (nuclear fraction) and the 164,000 X g supernatant fraction (cytosol) of homogenates of the sebaceous glands were used for measurements of androgen binding characteristics, using dextran-coated charcoal and sucrose gradient methods. Scatchard plots showed high affinity binding for [3H]dihydrotestosterone (DHT) and [3H]methyltrienolone (R1881). Nuclei prepared from bald scalp contained greater total androgen binding capacity than nuclei of hairy scalp, although Kd values of type I binding were similar (0.68 vs 0.56 nM, respectively). On sucrose gradient, the binding protein from cytosol was found in the 7 to 8S density range. Androgen binding by cytosol of sebaceous glands of hairy scalp had Kd of 1.89 +/- .79 and 2.05 +/- .56 nM for DHT and R1881, respectively, and Bmax of 18.7 +/- 4.4 and 20.0 +/- 4.6 fmol/mg protein for DHT and R1881, respectively. Cytosol from sebaceous glands of bald scalp had Kd values approximately half those of hairy scalp, and Bmax values 50%-100% higher. The bound 3H labeled DHT and R1881 could be partially displaced by testosterone (40-50%), moxestrol (28-32%), promegestone (19-26%), and delta 4-androstenedione (6-12%), but not by dehydroepiandrosterone. These data demonstrate the presence of specific androgen binding protein in sebaceous glands, and that sebaceous glands of bald scalp have greater binding affinity and capacity for androgens than those in hairy scalp. This difference may explain the greater androgenic response in androgenic alopecia.