Binding of Steroid Hormones by the 105,000 x g Supernatant Fraction from Homogenates of Rat Skin and Variations during the Hair Cycle

Examination of Fluconazole-Induced Alopecia in an Animal Model and Human Cohort

Fluconazole-induced alopecia is a significant problem for patients receiving long-term therapy. We evaluated the hair cycle changes of fluconazole in a rat model and investigated potential molecular mechanisms. Plasma and tissue levels of retinoic acid were not found to be causal. Human patients with alopecia attributed to fluconazole also underwent detailed assessment and in both our murine model and human cohort fluconazole induced telogen effluvium. Future work further examining the mechanism of fluconazole-induced alopecia should be undertaken.

The biological actions of estrogens on skin

There is still extensive disparity in our understanding of how estrogens exert their actions, particularly in non-reproductive tissues such as the skin. Although it has been recognized for some time that estrogens have significant effects on many aspects of skin physiology and pathophysiology, studies on estrogen action in skin have been limited. However, estrogens clearly have an important function in many components of human skin including the epidermis, dermis, vasculature, hair follicle and the sebaceous, eccrine and apocrine glands, having significant roles in skin aging, pigmentation, hair growth, sebum production and skin cancer. The recent discovery of a second intracellular estrogen receptor (ERbeta) with different cell-specific roles to the classic estrogen receptor (ERalpha), and the identification of cell surface estrogen receptors, has provided further challenges to understanding the mechanism of estrogen action. It is now time to readdress many of the outstanding questions regarding the role of estrogens in skin and improve our understanding of the physiology and interaction of steroid hormones and their receptors in human skin. Not only will this lead to a better understanding of estrogen action, but may also provide a basis for further interventions in pathological processes that involve dysregulation of estrogen action.

Estradiol distribution and penetration in rat skin after topical application, studied by high resolution autoradiography

Transdermal pathways and targets in the skin for estradiol were investigated using dry-mount autoradiography. 3H-estradiol-17 beta was applied at doses of 30.1 pmol, 120.4 pmol and 301 pmol/cm2 to shaved rat skin in the dorsal neck region. Vehicles were DMSO, ethylene glycol or sesame oil. After 2 h of topical treatment with 30.1 pmol 3H-estradiol x cm-2 dissolved in DMSO a distinct cellular distribution was apparent. Target cells with concentrations of radioactivity were found in epidermis, sebaceous glands, dermal papillae of hair and fibroblasts. After treatment with 120.4 and 301 pmol/cm2, a penetration gradient of radioactivity was recognizable however it masked specific cellular and subcellular uptake. The stratum corneum accumulated and retained radioactivity, apparently forming a depot for the hormone. Strong concentration and retention of the hormone was conspicuous in sebaceous glands for more than 24 h, suggesting that sebaceous glands serve as a second storage site for the hormone. In all autoradiograms two penetration pathways to the dermis were visible: one through the stratum corneum and epidermis, the other through the hair canals and hair sheaths.

Correlation of hepatic cytosolic androgen binding proteins with androgen induction of hepatic microsomal ethylmorphine N-demethylase in the rat

Previous reports have demonstrated the presence of moderate to high affinity binding for androgens in the cytosol of livers from male rats. This binding was significantly lower in female rats or in immature rats of either sex. The hepatic androgen binding protein, which sedimented at approx. 4 S on sucrose density gradients, has been called a receptor which mediates the actions of androgens in the liver. The experiments in the present study were designed to evaluate the hepatic androgen binding protein for characteristics which have been attributed to receptors in other tissues and to correlate the presence of androgen binding with androgen induction of hepatic drug metabolism. In the current studies, we have shown that cytosol from the livers of male rats bound [3H]dihydrotestosterone [( 3H]DHT) and translocated this steroid ligand to the nucleus in a time and temperature dependent manner. Cytosol prelabeled with [3H]DHT, when passed over a column of denatured DNA cellulose, eluted in three radioactive peaks. Two of these peaks were absent when cytosol from livers of female or hypophysectomized males was used. In addition, the presence of high concentrations of hepatic androgen binding correlated well with the ability of androgen to induce ethylmorphine N-demethylase, a marker of microsomal cytochrome P-450-dependent drug metabolism. Values for both parameters were higher in males than in either females or hypophysectomized males. Testosterone treatment induced both parameters in ovariectomized females and 17 beta-estradiol repressed both in males. However, testosterone treatment failed to induce hepatic androgen binding in hypophysectomized males and immature males, both of which are also unresponsive to androgen induction of drug metabolism. The results suggest that one or more hepatic cytosolic androgen binding proteins possess several characteristics associated with steroid receptors in reproductive tract tissue. Furthermore, this binding may be implicated as a mediator for the androgen induction of at least one component of hepatic drug metabolism.