Immunohistochemical evidence for differential distribution of 5 alpha-reductase isoenzymes in human skin.

Antibodies raised against fragments of synthetic peptides of human 5 alpha-reductase isoenzymes 1 (h5 alpha r1) and 2 (h5 alpha r2) were applied to paraffin sections of human skin (scalp, eyelid, lip, breast, scrotum). Immunoreactive sites were differentially distributed, in that h5 alpha r1 immunoreactivity was present in the nuclei of cells in the stratum germinativum (basal and lower portion of the spinous layer) of the epidermis, subepithelial fibroblasts, adipocytes, smooth muscle cells of the scrotal tunica dartos, basal cells of sebaceous glands, excretory duct cells of sweat glands, cells of the dermal papilla and fibrous and outer epithelial sheath of hair roots, as well as endothelial cells of small vessels and Schwann cells of cutaneous myelinated nerves. In contrast, immunoreactivity for h5 alpha r2 was found in the cytoplasm of the cells of the spinous layer (and far less intensely in the basal layer) of the epidermis, subepidermal fibrocytes, and especially in subcutaneous adipocytes. Immunoreactivity was strongest in the non-keratinized portion of the inner epithelial sheath and the cuticle of hair follicles, whereas other portions of the hair root were negative. Sweat glands were stained, whereas sebaceous glands showed only weak diffuse immunoreactivity. In mucocutaneous zones, salivary glands and conjunctival epithelium showed immunoreactive cells. Vascular endothelium displayed immunoreactivity only in the genital region. We present experimental evidence for a differential distribution of 5 alpha-reductase isoenzymes in human skin. This might reflect a diversity in the response of different areas of the skin to androgenic challenge.