ABSTRACTS 395 The sun protection substances not only delayed the skin cancer development, but also delayed the time of death of the animals irradiated with the ultravi- olet rays, UV stability of sunscreens? A model for in vitro testing H. U. Gonzenbach, Ph.D., G. Klecak, MD, and R. Schwarzenbach, Givaudan S.A., 5 Chemin de la Parfumerie, CH-1214 Vernier, Geneva, Switzer- land (H.U.G., R.S.), and F. Hoffmann-LaRoche & Co Ltd. (G.K.) The question whether a sunscreen molecule is pho- tostable or not is being raised more and more often. Simple U¾-absorption measurements before and after UV exposure cannot provide a reliable answer although suggested in the literature. Such single- point measurements do not allow to distinguish be- tween irreversible degradation (case I) and reversible changes such as double-bond isomerization (case II) leading to a stable photostationary equilibrium. A kinetic study is required or a cross-check by an in- dependent method (e.g., HPLC) in order to differ- entiate case I and II. An in vitro model is proposed featuring ease of kinetic studies and an optional possibility for HPLC analysis. Examples for both cases I and II were studied with this model under natural sunlight as well as with different artificial light sources. Methods for testing sunscreens: DIN versus FDA methods R. E. Davies, Ph.D., Temple University, 3322 North Broad Street, Philadelphia, PA 19140 The sun protection factor (SPF) is an indirect index of sunscreen efficacy. Such indices have general comparative value only if they are obtained under "comparable" conditions and if they reflect ade- quately the effects of significant variables. The two most widely used methods for estimating the SPF index differ significantly with respect to the radia- tion source and the rate of application of the test material. Theoretical considerations suggest that the DIN method may produce relatively lower nu- meric SPF values for sunscreens of low protective efficacy because of a lower application rate com- pared to the FDA method. Conversely, DIN meth- odology may produce relatively higher values for sunscreens of high efficacy because of the absence of longer wavelength radiation from its radiation source. Direct evaluation indicates that these ten- dencies may cancel, but it appears that achievement of equivalent estimates is fortuitous rather than in- evitable. Methodologies for testing sunscreen UVA pro- tection C. A. Cole, Johnson & Johnson Baby Products, Grandview Road, Skillman, N.J. 08558 Standard methodologies have been established for the determination of sunscreen efficacy against acute sunburn and yield the familiar sun protection factors (SPFs). This measure indicates primarily the protection provided by the sunscreen against ultra- violet B (UVB) radiation. Similar testing of UVA protection is much more difficult because of the low sensitivity of individuals to UVA radiation for acute reactions, namely erythema. To enhance the sensi- tivity of individuals to UVA radiation for sunscreen testing, phototoxic materials such as 8-methoxy- psoralen (8-MOP) or anthracene have been utilized. These two materials cause sensitivity in two dis- tinctly different regions of the UVA and would yield different protection factors when testing one sunscreen product. In addition, the choice of the irradiation source would also have a profound effect on the outcome of the test results. In vitro testing methodologies may offer a partial solution to this dilemma and will be discussed. SESSION D HAIR Research on the mechanism by which minox- idil stimulates hair growth Gerald R. Zins, Ph.D., Hairgrowth Research, The Upjohn Company, Henrietta Street, Kalamazoo, MI 49001 Clinically, minoxidil stimulates hair growth by in- creasing the proportion of follicles in anagen. Ini- tially, many supposed this was due to enhanced fol- licular blood flow. Indeed, minoxidil is quite unique among vasodilating agents in enhancing blood flow to the skin, but this hypothesis has not been supported in man. A basic question con- cerning how minoxidil works is whether the parent molecule or a metabolite is responsible. Minoxidil sulfate accounts for the relaxation of vascular smooth muscle and works by opening potassium channels in the cell membrane. It is not clear whether a similar action is exerted on the hair fol- licle either by minoxidil or its sulfated derivative. Nevertheless, both agents stimulate hair shaft growth in cultured follicles, making it clear that an action independent of vasodilitation is being ex- erted. Studies of gene expression suggest that min- oxidil's action in cultured follicles involves activa- tion at the beginning of a normal process of cell division.

396 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Dyestaining and the removal of cationics from keratin Clarence R. Robbins, Ph.D., Charles Reich, Ph.D., and Jane Clark, Ph.D., Colgate Palmolive Co., 909 River Road, Piscataway, N.J. 08854 The Red 80 dye staining procedure has been modi- fied to help serve as a tool to study the removal of cationic surfactants from keratin surfaces. Results from this method and radiotracer studies demon- strate that monofunctional cationic surfactants are not completely removed from hair by washing with anionic detergents. Shorter chain length anionics are more efficient for removing cationics than longer chain length anionics. When washing hair with sodium lauryl sulfate, significantly more lauryl sulfate is left behind on hair previously treated with cationic detergent than on hair con- taining no cationic detergent. Lipid components of conditioning products adsorb onto hair along with cationic actives. The ratio of lipid/cationic adsorbed increases with the ratio of lipid/cationic in the for- mulation. Conditioner lipids, to a certain extent, facilitate removal of the cation from the substrate however, evidence also suggests that they partici- pate in anionic detergent buildup on hair. Fully formulated conditioner products behave analo- gously to the binary systems containing cationic and lipid. Mechanisms will be proposed to provide working models to help explain these results. A contribution to understanding the nature of hair color L. Albrecht, S. K. Kurtz, Ph.D., and L. J. Wol- fram, Ph.D., Clairol, Inc., 2 Blachley Road, Stam- ford, CT 06922 A physicochemical model of natural hair color based on calculation of the diffuse reflectance of melanin dispersions in a keratin matrix has been developed. Using the results of exact Mie calculations of the scattering and absorption cross sections for indi- vidual pigment granules present in hair, we show that hair color is strongly influenced by the number and size of the pigment particles present in hair, number and size of voids, as well as the optical characteristics of the melanin (optical band gap). Experimental supports for the model stems from the measurements of the pigment particle distribution in hair of differing colors as well as from the direct color evaluation using diffuse reflectance spectro- photometry. Regulation factors controlling the androgen re- ceptor protein in isolated human hair follicles Marty E. Sawaya, M.D., Ph.D., Leonard Lewis, M.D., and S. L. Hsia, Ph.D., University of Miami, Department of Dermatology, P.O. Box 016960 R-117, Miami, FL 33101 Our present work involves using human tissue from hair transplant surgery to study the biochemical mechanisms involved in male pattern baldness. Iso- lated human hair follicles and sebaceous glands from scalp tissue were used to purify the male hor- mone receptor protein. Anagen and telogen hair follicles were used from the same individuals (60 patients) and compared for the content of androgen receptor protein. Our results found two forms of the androgen receptor protein, as well as two regulation proteins that control the receptor protein. The reg- ulation factors, called converting factor and inhib- itor protein, are found in active growing hair fol- licles. Further investigations of these factors are in progress and may indicate a more successful means of controlling these androgen-dependent skin dis- orders.