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J. Cosmet. Sci., 60, 415–422 (July/August 2009) 415 Skin collagen reproduction increased by ascorbic acid derivative iontophoresis by frequent-reversal bipolar electric stimulation YUSUKE HORI, RYUJI AKIMOTO, AKIKO HORI, KATSUHIKO KATO, DAISUKE CHINO, SHOHEI MATSUMOTO, SHOHEI KAMIYA, and YASUO WATANABE, Tes Holdings Co., Ltd, Tokyo 111-0032 (Y.H) Homer Ion Laboratory Co., Ltd, Tokyo 150- 0045 (R.A., S.K.) Gene Expression and Regulation, Institute of Medical Science, University of Tokyo 108-8639 (A.H.) Department of Genetical Education, School of Veterinary Medicine, University of Azabu, Kanagawa 229-8501 (K.K.) Department of Pharmacology and Pharmacotherapy, School of Medicinal Pharmacy, Nihon Pharmaceutical University, Saitama 362-0806 (D.C.,Y.W.) and Department of Anesthesiology, Tokyo Medical University, Tokyo 160-0023 (S.M.), Japan. Accepted for Publication February 11, 2009. Synopsis The effect of the iontophoresis of ascorbic acid (Vitamin C VC) derivative with frequent-reversal bipolar electric stimulation on the production of collagen in rat skin was evaluated in terms of hydroxyproline con- tent through high-performance liquid chromatography. First, a control group was not given electrical stimu- lation and four groups were stimulated with a unipolar pulse for 0.5–10 min every day for one week. The hydroxyproline level in the skin was increased depending on the length of the stimulation. Second, a control group was not given any electrical stimulation, and three groups were treated with (a) VC solution without any stimulation, (b) a bipolar pulse for 10 min with saline, or (c) a bipolar pulse for 5 min with the VC solu- tion. Signifi cant increases were found in all the stimulation groups, although these treated with the VC solution without any stimulation did not have any effects compared to the control. Thus, in order to increase the hy- droxyproline levels in skin, a VC must be delivered with bipolar stimulation as a method of iontophoresis. These results suggest that our newly developed electric stimulation is effective at increasing skin collagen content, and that bipolar stimulation is more effective on the iontophoresis of not only VC but also some medicines such as low- and high-molecular drugs directed to the target organ (7). INTRODUCTION Collagen is a major constituent of the dermis, and is therefore involved in many facets of skin disease as well as the recovery process. Collagen also plays an important role in main- taining the moisture content and the elasticity of skin, although collagen is altered and