SKIN MOISTURIZATION: LONG-TERM RESULTS 33 designs since they have been shown to influence the readings (21). Nonetheless, even in studies of moisturization by occlusive treatments, electrical measurements may prove a valuable adjunct to the visual assessment of skin condition. REFERENCES (1) E. Berardesca, EEMCO guidance for the assessment of stratum corneum hydration: Electrical methods, Skin Res. Technol., 3, 126-132 (1997). (2) H. Tagami, "Measurement of Electrical Conductance and Impedance," in Handbook of Non-Invasive Methods and the Skin, J. Setup and G. Jemec, Eds. (CRC Press, Boca Raton, FL, 1995), 10p. 159-164. (3) M. Loden, Biophysical methods of providing objective documentation of the effects of moisturizing creams, Skin Res. Technol., 1, 101-108 (1995). (4) A.O. Barel, P. Clarys, and B. Gabard, "In Vivo Evaluation of the Hydration State of the Skin: Measurements and Methods for Claim Support," in Cosmetics: Controlled Efficacy Studies and Regulation, P. Eisner, H. F. Merk, and H. I. Maibach, Eds. (Springer-Verlag, Berlin, 1999), 10p. 57-80. (5) J. W. Fluhr, M. Gloor, S. Lazzerini, P. Kleesz, R. Grieshaber, and E. Berardesca, Comparative study of five instruments measuring stratum corneum hydration (Corneometer CM 820 and CM 825, Skicon 200, Nova DPM 9003, DermaLab). Part I. In Vitro, Skin Res. Technol., 5, 161-170 (1999). (6) P. Clarys, A. O. Barel, and B. GabaM, Non-invasive electrical measurements for the evaluation of the hydration state of the skin: Comparison between three conventional instruments--the Corneometer, the Skicon and the Nova DPM, Skin Res. Technol., 5, 14-20 (1999). (7) W. Courage, "Hardware and Measuring Principle: Corneometer," in Bioengineering of the Skin: Water and the Stratum Corneum, P. Eisner, E. Berardesca, and H. I. Maibach, Eds. (CRC Press, Boca Raton, FL, 1994), pp. 171-175. (8) H. Tagami, "Hardware and Measuring Principle: Skin Conductance," in Bioengineering of the Skin: Water and the Stratum Comeurn, P. Eisner, E. Berardesca, and H. I. Maibach, Eds. (CRC Press, Boca Raton, FL, 1994), pp. 197-203. (9) B. Gabard and P. Treff$1, "Hardware and Measuring Principle: The NOVA DPM 9003," in Bioengi- neering of the Skin: Water arid the Stratum Corneum, P. Eisner, E. Berardesca, and H. I. Maibach, Eds. (CRC Press, Boca Raton, FL, 1994), pp. 177-195. (10) G. L. Grove, M. J. Grove, C. Zerweck, and E. Pierce, Comparative metrology of the evaporimeter and the DermaLab TEWL probe, Skin Res. Technol., 5, 1-8 (1999). (11) G. L. Grove, M. J. Grove, C. Zerweck, and E. Pierce, Computerized evaporimetry using the DermaLab TEWL probe, Skin Res. Technol., 5, 9-13 (1999). (12) J. Pinnagoda, R.A. Tupker, R.A. Agner, and J. Serup, Guidelines for transepidermal water loss (TEWL) measurement, Contact Dermatitis, 22, 164-178 (1990). (13) J. Pinnagoda, "Hardware and Measuring Principles: Evaporimeter," in Bioengineering of the Skin: Water and the Stratum Corneum, P. Elsner, E. Berardesca, and H. I. Maibach, Eds. (CRC Press, Boca Raton, FL, 1994), pp. 51-58. (14) J. Setup, EEMCO guidance for the assessment of dry skin (xerosis) and ichthyosis: Clinical scoring systems, Skin Res. Technol., 1, 109-114 (1995). (15) D. L. Bissett and J. F. McBride, Skin conditioning with glycerol,J. Soc. Cosmet. Chem., 35,345-350 (1984). (16) M.D. Batt, W. B. Davis, W. A. Gerrard, and B. D. Ridge, Changes in the physical properties of the stratum corneum following treatment with glycerol,J. Soc. Cosmet. Chem., 39, 367-381 (1988). (17) D. H. Powers and C. Fox, The effect of cosmetic emulsions on the stratum corneum, d. Soc. Cosmet. Chem., 10, 109-116 (1959). (18) M. M. Rieger, Skin, water and moisturization, Cosmet. Toiletr., 104, 41-51 (1989). (19) I. H. Blank, Factors which influence the water content of the stratum conreum,J. Invest. Dermatol., 18, 433-440 (1952). (20) H. Tagami, Quantitative measurements of water concentration of the stratum corneum in vivo by high-frequency current, Acta Derm. Vernereol. Suppl. (Stockh.), 185, 29-33 (1994). (21) M. Loden and M. Lindberg, The influence of a single application of different moisturizers on the skin capacitance, Acta Derre. Venereol., 71, 79-82 (1991).

Cosmet. Sd., 52, 35-50 (January/February 2001) Kinetics of permeation and metabolism of -tocopherol and -tocopheryl acetate in micro-Yucatan pig sin MEERA RANGARAJAN and JOEL L. ZATZ, Rutgers-The State University of New Jersey, Department of Pharmaceutics, College of Pharmacy, 160 Frdinghuysen Road, Piscataway, NJ 08854-8020. Accepted for publication January 15, 2001 Synopsis The objective of this research was to investigate the permeation and metabolism of o•-tocopheryl acetate (tx-TAc) and tx-tocopherol (ix-T) from solution and emulsion formulations and to delineate the kinetics of such metabolism. Simple formulations containing tx-TAc and tx-T were applied to fresh, viable micro-Yucatan skin derma- tomed to a thickness of 250-300 pro, as a finite dose in a flow-through diffusion system. The experiments were stopped at time intervals of 2, 6, 12, and 24 hours. At the end of each time interval, the amounts removed by washing, retained in the stratum corneum (SC), and penetrated into the viable skin and receptor were determined by a validated HPLC method. Receptor concentrations were below the limit of detection. tx-TAc underwent metabolism in pig skin to the active antioxidant tx-T. The metabolite appeared as early as two hours after application. The extent of metabolism was highest at 6-12 hours after application. No metabolism was detected in the stratum corneum. Delivery of tx-T from isopropyl myristate (IPM) solution was more efficient than utilization of tx-TAc from the same solution. Approximately 1.5% of tx-T yielded the same viable skin concentration as 5% tx-TAc. Topical application of tx-tocopherol or its prodrug acetate was capable of enhancing the overall antioxidant capacity of pig skin. The hydrolyric pathway of tx-TAc leading to the active antioxidant tx-T could possibly be saturable. INTRODUCTION Most skin cancers and other symptoms of cutaneous aging are the result of exposure to solar radiation. Evidence for free radical formation in UV-radiated skin (1) provided the basis for implication of reactive oxygen species in UV-mediated cutaneous damage including skin cancer, autoimmune diseases, phototoxicity, photosensitivity, and skin aging. A number of antioxidants that possess oxygen radical scavenging properties have been tested as potentially beneficial photoprotective agents (2,3). o•-Tocopherol (o•-T) Address all correspondence to Meera Rangarajan. Telephone: 732-342-9884 email: meerarc@hotmail.com fax: 732-445-3134. 35