Androgen receptors are only present in mesenchyme-derived dermal papilla cells of red deer (Cervus elaphus) neck follicles when raised androgens induce a mane in the breeding season

Red deer stags produce an androgen-dependent mane of long hairs only in the breeding season; in the non-breeding season, when circulating androgen lev els are low, the neck hair resembles the rest of the coat. This study was d esigned to determine whether androgen receptors are present in deer follicl es throughout the year or only in the mane (neck) follicles when circulatin g testosterone levels are high in the breeding season. Although androgens r egulate much human hair growth the mechanisms are not well understood; they are believed to act on the hair follicle epithelium via the mesenchyme-der ived dermal papilla. The location of androgen receptors in the follicle was investigated by immunohistochemistry and androgen binding was measured bio chemically in cultured dermal papilla cells derived from mane and flank fol licles during the breeding season and from neck follicles during the non-br eeding season. Immunohistochemistry of frozen skin sections using a polyclonal antibody to the androgen receptor localised nuclear staining only in the dermal papill a cells of mane follicles. Saturation analysis assays of 14 primary dermal papilla cell Lines using [H-3]-mibolerone demonstrated high-affinity, low-c apacity androgen receptors were present only in mane (breeding season neck) cells; competition studies with other steroids confirmed the specificity o f the receptors. Androgen receptors were not detectable in cells from eithe r the breeding season flank nor the non-breeding season neck follicles. The unusual biological model offered by red deer of androgen-dependent hair being produced on the neck in the breeding, but not the non-breeding seaso n, has allowed confirmation that androgen receptors are required in follicl e dermal papilla cells for an androgen response; this concurs with previous human studies. In addition, the absence of receptors in the non-breeding s eason follicles demonstrates that receptors are not expressed unless the fo llicle is responding to androgens. Androgen receptors may be induced in man e follicles by seasonal changes in circulating hormone(s).