TROPHIC EFFECTS OF ESSENTIAL FATTY-ACIDS ON PIG SKIN

The daily oral administration of 3 ml of two oils (So-5407 and So-1129 ) containing essential fatty acids (EFAs) for 16 weeks resulted in a t ransient increase in cell proliferative activity in the skin of female Large White pigs. The So-5407 oil contained 7% gamma-linolenic acid ( GLA) whereas So-1129 was an oil of similar composition, but with no GL A. Hyperplasia of the epidermis was observed after the administration of both oils, and this was characterized by an increase in the size of the rete pegs. The maximum effect occurred at 4 weeks after the start of oil administration, at which time the number of viable cell layers had increased by a factor of approximately 1.5, and mean epidermal th ickness (excluding the stratum corneum) was approximately 40% greater than that of the epidermis prior to oil administration. There was a ma rked increase in the labelling index (LI) of the basal cell layer of t he epidermis in pigs receiving So-5407. Maximum LIs were quantified at 4 weeks after the start of administration and were 18.8 +/- 1.3% and 13.1 +/- 1.7% for pigs receiving So-5407 and So-1129, respectively. Af ter this time the LI declined prgressively and had returned to values within normal limits (P > 0.1) by 8 weeks after the start of administr ation of both oils. A similar pattern of change in the LI was seen in the follicular epithelium, although the peak values at 4 weeks after t he start of oil administration of 12.2 +/- 1.8% and 10.8 +/- 0.9 for t he groups receiving So-5407 and So-1129, respectively, were lower than in the epidermis. Labelled cells were also counted in the papillary d ermis and maximum values were again seen at 4 weeks after the start of oil administration. Of the two oils, So-1129 had the greatest effect, with the number of labelled cells in the papillary dermis being a fac tor of three to four-fold higher than in skin prior to oil administrat ion, between 2 and 12 weeks after the start of administration.