HUMAN HAIR FOLLICLES 913 0 epiondrosterone Figure 5. Prcsumcd pathways of testosterone metabolism in hair follicles balance (Table VI). Thus, these data suggest that mainly growing hair follicles are affected by the tissue-active androgen whereas the resting follicles catabolize testosterone to androstenedione which is a relatively inactive androgen. In Fig. 5, the different pathways of testosterone in hair follicles are summarized. Only traces of epiandro- sterone, androsterone, and androstanediol were detectable when testos- terone was used as the substrate. Normal skin does not produce 5•-metabolites (25). In addition to the increase in pentose cycle activity, we must con- sider the possible increase in TPNH generating systems (such as the isocitrate dehydrogenase and •nalic dehydrogenase reactions in the grow- ing hair follicles) that increase synthesis of the active form of the hormone from testosterone.* Further experimental evidence is required to de- termine whether these speculations are correct. At present, we have solid proof only that human hair follicles actively metabolize testosterone in vitro with a major product being androstenedione, that they can pro- duce 5a-dihydrotestosterone at a rate comparable to that of the prostate, and that they contain sufficient 5a-reductase activity to account for the formation of this tissue-active androgen. * We are unable to dctect transdehydrogcnasc activity in human hair follicles. Therefore, the balance of pyridine nucleotides should be kept shifting to an excess of TPNH. Unpub- lished observation by K. Adachi.

914 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS ENZYMATIC BASIS FOR HORMONAL CONTROL OF HAIR FOLLICLE METABOLISSI One o[ the most significant biological contributions in the last decade is the discovery ot adenosine-3', 5'-cyclic-monophosphate (cyclic AMP) as a common mediator for different hormones working at their re- spective target tissues (32, 33). For example, the action of adrenocortico- tropic hormone (ACTH) on adrenal cortex, and of thyroid-stimulating hormone on thyroid gland, causes the same intracellular response in their respective tissues--a rapid increase in cyclic AMP. This increase in cyclic AMP influences a variety ot biochemical processes, such as increases in glucose oxidation, lipolysis, steroidogenesis, etc. The intracellular con- centration of cyclic AMP is regulated by the synthetic enzyme, adenyl cyclase, and the degradative enzyme, a specific phosphodiesterase. Nearly all hormones stimulate adenyl cyclase rather than inhibit phosphodiester- ase, with a subsequent increase in the intracellular level ot cyclic AMP (32,33). Notwithstanding the rapid accumulation ot literature on the role ot adenyl cyclase and cyclic AMP in the past five years, the existence ot this important mediator has not been reported in skin and its append- ages. Accordingly, we began to test the hypothesis that human scalp hair tollicles, particularly those ot the male, must contain adenyl cyclase, the activity ot which must be influenced by the tissue-active sex hormones. Preliminary data thus far obtained indicate that our assump- tion is correct.* To prepare crude adenyl cyclase, [Tesh hair follicles were obtained by plucking 50 to 100 gTowing scalp hairs, and homogenizing them in a medium consisting of 0.25M sucrose, lmM EDTA, lmM MgCI_% and 0.2M tris-HC1 buffer, pH 7.4. The homogenate was centrituged at 12,000 g for 10 rain at 4øC. The precipitate was washed twice with 0.25M sucrose and resuspended with appropriate amounts of water. Five •1 of an assay reagent mixture, slightly modified from that of Krishna (34), (e.g., 10 times increased amounts of ATP-•4C), were added to 5 •1 of this crude particulate preparation. This mixture was incubated for 3 hours at 37øC with and without additions of sex hormones. The resulting cyclic AMP was isolated by thin-layer chro- matography as described by Tao and Lipmann (35). * To be reported elsewhere in detail by K. Adachi and M. Kano.