title: Follicles play an important role in percutaneous absorption.
abstract: The relative importance of stratum corneum and follicles in percutaneous absorption is not fully understood. In order to quantitatively investigate the importance of the transappendageal route, we have previously developed a model of skin without follicles regrown dorsally on the hairless rat. Percutaneous absorption was compared, using a diffusion cell, in appendage-free skin relative to normal skin, and a predominant role of follicles for in vitro diffusion of [3H]hydrocortisone was noted. Results presented here of in vitro diffusion of tritiated hydrocortisone, niflumic acid, caffeine, and p-aminobenzoic acid, applied in acetone, confirm that appendageal diffusion is the major pathway in hairless rat skin. In the absence of follicles, the steady-state flux and the amounts diffusing in 24 or 48 h are 2-4 times lower than in normal skin. These results were confirmed in a second model in which diffusion of [3H]hydrocortisone was studied on skin samples taken one day after birth, at which time rat skin is still devoid of follicles, relative to five-day postnatal skin samples, in which follicles are fully developed. The steady-state flux and the total diffusion in 24 h were fivefold lower in follicle-free skin. These results support the view that follicles may have a far greater importance in percutaneous absorption than is generally assumed.
authors.affiliation: Centre International de Recherches Dermatologiques (C.I.R.D.), Valbonne, France.
authors.forename: B
authors.initials: B
authors.lastname: Illel
authors.forename: H
authors.initials: H
authors.lastname: Schaefer
authors.forename: J
authors.initials: J
authors.lastname: Wepierre
authors.forename: O
authors.initials: O
authors.lastname: Doucet
mesh_terms: D010129:4-Aminobenzoic Acid / Q000493:pharmacokinetics; D000818:Animals; D000831:Animals, Newborn / Q000378:metabolism; D002110:Caffeine / Q000493:pharmacokinetics; D004058:Diffusion; D006197:Hair / Q000378:metabolism*; D006854:Hydrocortisone / Q000493:pharmacokinetics; D066298:In Vitro Techniques; D009544:Niflumic Acid / Q000493:pharmacokinetics; D010539:Permeability; D051381:Rats; D011919:Rats, Inbred Strains; D012869:Skin Absorption
chemical_list: D002110:Caffeine; D009544:Niflumic Acid; D010129:4-Aminobenzoic Acid; D006854:Hydrocortisone