Percutaneous absorption and distribution of (14)C-gamma-linolenic acid in hairless rats and man.
Summary Deficiency of gamma-linolenic acid (gamma-LA), an essential fatty acid (EFA) in animals, provokes cutaneous disorders such as scaly lesions of the skin, acanthosis, loss of elasticity of the skin and irregularities in cutaneous barrier function. These disorders disappear with restitution of EFA. Although the deficiency does not exist in man, EFA could be of interest in cosmetology and dermatology, particularly in the treatment of dryness of the skin and some other cutaneous disorders observed in skin ageing. The efficiency of this treatment depends on an adequate cutaneous absorption of the acids. Experiments were performed with 4%(14)C-gamma-LA incorporated in an O/W emulsion and applied to the skin. Detection of gamma-LA was only in the superficial epidermal structures and in the sebaceous glands, as shown by autoradiography obtained with hairless rat skin sections. On human skin in vitro, by using the stripping technique, very slow diffusion into cutaneous structures was observed during the first 2 hours. Eighteen percent of skin radioactivity was found in Malpighian layers after 8 hours. Permeability constants were measured in vitro with diffusion cells. In hairless rats 18 months old, Kp was 4.6 x 1(-6) cm h'. This value was 31 x 10(-6) cm h-(-1) in rats of the same age deficient in EFA. With human skin, the permeability constant after 24 hours was in the same range as that in normal rats (4.67 x 1C6 cm h(-1)). During this time, 0.5% of gamma-LA was absorbed. In anaesthetized hairless rats, 18 months old, the radioactivity in plasma, liver, kidney, muscular and fatty tissues remained negligeable up to 8 hours after cutaneous administration of gamma-LA. On the contrary, radioactivity was high-Kder the m a of application and increased with time in subcutaneous conjunctive tissue (9 mug/g(-1) after 8 hours) and muscular tissue. These results show the potential importance of the use of gamma-LA in dermatology and cosmetology.
Costedoat
M
M
Laboratoire de Pharmacodynamie-Centre d'Etudes Pharmaceutiques, 92290 - Châtenay-Malabry, France.
Rolez
S
S
Wepierre
J
J