PROPERTIES OF or- AND [3-GLYCYRRHIZINS 189 general manager of our laboratory, to Mr. M. Yamagishi, general manager of our labo- ratory, and to Mr. T. Yoneya who encouraged us throughout this work. REFERENCES (1) H. Fujita, T. Sakurai, M. Yoshida, and S. Toyoshima, Antiinflammatory effect ofglycyrrhizinic acid. Effects of glycyrrhizinic acid against carrageenin-induced edema, UV-erythema and skin reaction sensitized with DNCB, Pharmacometrics, 19, 481-484 (1980). (2) A. Otsuka, Y. Yonezawa, K. Iba, T. Tatsumi, and H. Sunada, Physico-chemical properties of gly- cyrrhizic acid in aqueous media. I. Surface-active properties and formation of molecular aggregates, Yakugaku Zasshi, 96, 203-208 (1976). (3) A. Otsuka, Y. Yonezawa, and Y. Nakamura, Physicochemical properties of glycyrrhizic acid in aqueous media. II. Effect of flocculation-deflocculation behavior of suspensions of sulfathiazole and graphite, J. Pharm. Sci., 67, 151-154 (1978). (4) Y. Yonezawa and A. Otsuka, Physico-chemical properties of glycyrrhizic acid in aqueous media. III. Solubilizing properties for dyes and medicinal substance, Yakugaku Zasshi, 101, 829-835 (1981). (5) B. E. Azaz and R. Segal, Glycyrrhinzin as gelling agent, Pharm. Acta Helv., 55, 183-186 (1980). (6) A. Miyashita, K. Imoto, T. Kuramoto, K. Kakegawa, and Y. Otani, Reaction ofglycyrrhizic acid. I. Base-catalyzed isomerization. Abstracts of papers, The 100th Annual Meeting of the Pharmaceutical Society of Japan, Tokyo, April 1980, p 202. (7) K. Tsubone, S. Ohnishi, and T. Yoneya, Separation of glycyrrhizinic acid isomers by high-perfor- mance liquid chromatography, J. Chromatogr., 248, 469-471 (1982). (8) A. F. Cockerill, G. L. O. Davies, R. C. Hardon, and D. M. Rockham, Lanthanide shift reagents for NMR spectroscopy, Chem. Rev., 73, 553-588 (1973). (9) H. Yoshioka, K. Honda, and M. Kondo, Spin probe study of the aqueous solutions of or- and [3-glycyrrhizins,J. Colloid Interface Sci., 93, 540-544 (1983).

j. Soc. Cosmet. Chem., 37, 191-198 (May/June 1986) !n vivo cutaneous distribution of linoleic acid following topical application in the hairless rat J. WEPIERRE and M. CORROLLER, Laboratoire de Pharmacologie, Universitg Paris-Sud, rue J. B. Clgment, 92290 Chatenay Malabry, France D. DUPUIS, A. ROUGIER, and C. BERREBI, Laboratoire d'Absorption percutange et d'Histologie, Centre de Recherche Fondamentale de l'Oreal, 1 avenue Saint Germain, 93601 Aulnay sous Bols, France. Received December 30, 1985. Synopsis Hairless rats were treated by single or iterative applications on the skin with an emulsion containing 153 of '4C labeled linoleic acid in order to test whether this compound becomes localized in epidermal and derreal layers. The distribution of radioactivity within the skin was investigated in the horny layer by stripping and in the epidermis and the dermis by cutting slices parallel to the cutaneous surface. In the horny layer, total amounts of labeled products remained constant 24 h after single application and 24 and 72 h after iterative applications. Thus a reservoir of linoleic acid was demonstrated in the stratum corneum. In the epidermis and dermis, the concentration of linoleic acid increased with time. It was always smaller in the epidermis than in the dermis where storage in the vicinity of the sebaceous glands appears to Occur. The retention of linoleic acid in the horny layer and in the sebaceous area of the dermis might explain in part the findings of others that it has a specific localized action in the skin appearing to correct the cutaneous symptoms in essential fatty acid deficient animals. INTRODUCTION Linoleic acid is an important essential fatty acid (EFA). Its bioconversion to •/linolenic acid is the first absolute step leading to arachidonic acid synthesis (1). In some patho- logical cases, this bioconversion is defective so that chronic squamous dermatosis has been observed in man (2). In EFA-deprived animals, several disorders of the keratiniza- tion processes appear in the epidermis such as acanthosis, hyperkeratosis, and a high level of transepidermal water loss (3-6) while DNA synthesis increases (3,6,7). More- over, sebaceous glands are hypertrophied. (!,6). Topical application of linoleic acid (or its metabolites) may correct these deficiency effects (8-11). It has been shown that percutaneously applied •/ linolenic acid in the hairless rat in vivo (12) or linoleic acid in man in vitro (13) were locally concentrated in epidermal and dermal tissues while their plasma and urine levels stayed very low. In order to more completely test EFA-specific action, we have investigated the linoleic 191