Properties and dynamics of glucocorticoid binding capacity in rat skin

Effect of RU 486 on the atrophogenic and antiinflammatory effects of glucocorticoids in skin

Clobetasol-17-propionate (CP), a synthetic glucocorticoid (GC), reduced skin thickness in rats. Both the subcutaneous injection and topical applications of RU 486 counteracted CP-induced reduction in skin thickness. Topical application of the CP cream completely inhibited the ear edema produced by croton oil. A less potent GC, hydrocortisone-17-butyrate, also inhibited ear edema. This antiinflammatory effect was not abolished by the subcutaneous injection or topical application of RU 486. These observations suggest that GC-induced skin atrophy is mediated by glucocorticoid receptors (GRs), while the inhibition of croton oil-induced inflammation by GC is primarily related to the direct effects of GC, which are not mediated by GRs. Our findings suggest that RU 486 inhibits the atrophogenic effect of GCs without interfering with their antiinflammatory effect. Dissociation of antiinflammatory and atrophogenic activity of GC seems favorable in treating inflammatory skin diseases lacking epidermal proliferation.

Binding affinities of mometasone furoate and related compounds including its metabolites for the glucocorticoid receptor of rat skin tissue

The binding affinities of mometasone furoate (MF), its metabolites and related compounds for the glucocorticoid receptor of rat epidermis and dermis were measured. MF and its main metabolite exhibited binding affinities higher than those of alclomethasone dipropionate (ADP) and betamethasone dipropionate (BDP), but equivalent to betamethasone 17-valerate (BMV). For compound I (metabolite of MF), ADP, BDP and BMV, the binding affinity was found to be higher in epidermis relative to dermis. This difference in the dermal/epidermal binding ratio may be a favorable sign leading to a possible reduction of dermal collagen atrophy, a known side effect of glucocorticoids. In structure-binding relationship studies, esterification of the 17-OH by furoylation and introduction of the 9 alpha-Cl caused a marked increase of the binding affinity, whereas the 6 beta-hydroxylation led to a pronounced decrease.

Epidermal and hepatic glucocorticoid receptors in cats and dogs

Low capacity, high affinity [3H] dexamethasone binding receptors were identified in cytosolic preparations of liver (mean number 45 +/- 10.1 fmol mg-1 protein, apparent dissociation constant 0.4 +/- 0.1 nM) and skin (mean number 46.4 +/- 23.8 fmol mg-1 protein, apparent dissociation constant 1 +/- 0.2 nM) of clinically normal dogs. For clinically normal cats, approximately half these numbers of receptors with a lower affinity, were detected in liver (mean number 23.1 +/- 10.4 fmol mg-1 protein, apparent dissociation constant 3.2 +/- 0.9 nM) and skin (mean number 23.90 +/- 10.9 fmol mg-1 protein, apparent dissociation constant 2.2 +/- 1.5 nM). This difference between dogs and cats in [3H] dexamethasone binding receptors may contribute to the relative glucocorticoid resistance observed in cats.

Induction of ethoxyresorufin-O-deethylase and inhibition of glucocorticoid receptor binding in skin and liver of haired and hairless HRS/J mice by topically applied 2,3,7,8-tetrachlorodibenzo-p-dioxin

The biochemical changes associated with the toxicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) have been reported to include alterations in glucocorticoid and epidermal growth factor receptors and mixed function oxidase (MFO) induction. TCDD induces MFO activity in skin of both haired and hairless HRS/J mice. However, epidermal hyperplasia and hyperkeratosis are produced only in the skin of hairless mice. Therefore, since steroid and growth factor responses are implicated in cell proliferation and differentiation, these mice constitute a model system for assessing the possible roles of glucocorticoid and epidermal growth factor receptors in the toxicity of TCDD. The effect of dermal TCDD application (12 micrograms/kg in 100 microliters acetone) on ethoxyresorufin-O-deethylase (EROD) activity, glucocorticoid receptor binding and epidermal growth factor receptors in liver and skin of hairless and haired mice was determined. No differences existed in the basal number of cytosolic glucocorticoid receptors (Bmax) or the apparent equilibrium binding constants (Kd) in control liver, dorsal skin and abdominal skin of male and female hairless mice and haired male mice. Seven days after topical application of TCDD, decreases of approximately 38% were observed in the hepatic Bmax of the glucocorticoid receptors in both haired and hairless mice. However, in dorsal skin, TCDD decreased Bmax by approximately 40% in hairless mice but only 18% in haired mice. The dexamethasone-glucocorticoid receptor complex from both liver and skin of control and TCDD treated mice had similar sedimentation co-efficients in sucrose density gradients. TCDD had no effect on the Kd of glucocorticoid receptors of skin or liver in haired and hairless mice. No difference was observed in the time-dependent increases in hepatic EROD activity between haired and hairless mice after dermal application of TCDD. However, the maximum induction of EROD activity in microsomes from the skin of haired mice was only 60% of the activity observed in hairless animals. The induction of EROD by TCDD did not correlate temporally with the decrease in glucocorticoid receptor binding. The application of TCDD to the skin of hairless mice resulted in epidermal hyperplasia and dermal keratinization, while little change was observed in the general morphology of the skin of haired mice following dermal application. The application of TCDD had no effect on the incidence and distribution of epidermal growth factor receptors in skin of haired and hairless mice as determined immunohistochemically. Thus, the biochemical effects of TCDD are not only strain dependent, but tissue specific. Furthermore, decreases in glucocorticoid and epidermal growth factor receptors do not appear to be general markers of TCDD toxicity.