Corticoids and cultured human epidermal keratinocytes: specific intracellular binding and clinical efficacy

Cytosol of cultured human epidermal keratinocytes contains macromolecules, that bind corticoids with high affinity. Binding constants were in the same range for cultured keratinocytes originating from different individuals and did not change during serial cell cultivation. At 0 degree C and using 3H-triamcinolone acetonide as ligand, we obtained the following values; apparent Bmax = 160- 250 fmoles/mg protein and Kdiss = 3.1-5.0 nM; with 3H-dexamethasone Bmax = 200-350 fmoles/mg protein, Kdiss = 6.0-11.1 nM, and with 3H-hydrocortisone Bmax = 140-220 fmoles/mg protein, Kdiss = 17-25 nM. There was an indication that the binding capacity of the receptor system is higher the younger the age of the skin donor. A number of steroids and corticoids commonly used in dermatological practice were tested with respect to displacement of 3H-triamcinolone acetonide, 3H-dexamethasone, and 3H-hydrocortisone from binding sites in cytosol. Good correlation between clinical efficacy and specific binding was observed for all 3 ligands. Other steroids such as 17-beta estradiol and nandrolone did not show any affinity for the corticoid binding system. Progesterone displace 3H-corticoids from their binding sites, but the IC50 was of one order of magnitude larger.