LOCALIZATION AND REGULATION OF EXPRESSION OF THE FAR-17A GENE IN THE HAMSTER FLANK ORGANS

A quantitative in situ hybridization study was carried out to determin e the precise localization and androgen regulation of the flank organ regulated (FAR-17A) mRNA expression in the different cellular componen ts of the hamster flank organs. Although FAR-17A mRNA was highly expre ssed in the epithelial cells of the sebaceous glands, it was also foun d in the outer root sheath of the hair follicles and in melanocytes. T he changes in FAR-17A mRNA levels, in the size of the flank organ and sebaceous gland areas as well as in the weight of the seminal vesicles and prostate, were compared following castration and after 5 alpha-di hydrotestosterone treatment. FAR-17A mRNA levels were already signific antly decreased 1 d after castration, in parallel with a concomitant d ecrease in the number of labeled cells with the FAR-17A probe. A maxim al decrease was found 7 d after castration. The other parameters were significantly reduced later. After 7 d of treatment with dihydrotestos terone, all values returned to those found in intact animals. Similar stimulatory effects on these parameters were observed after treatment with the adrenal sex steroid precursor dehydroepiandrosterone, These d ata show that all of the components of the flank organs (sebaceous gla nds, hair follicles, and melanocytes) express the flank organ regulate d (17A) type gene (FAR-17A) gene and that its expression is stimulated by treatment with either dihydrotestosterone or dehydroepiandrosteron e. Moreover, FAR-17A mRNA levels respond to androgen stimulation more rapidly than the standard morphologic parameters, revealing that the F AR-17A gene could be a more sensitive and cell specific marker to stud y tile mechanisms of androgen action in the skin.