Incorporation of I-14C-acetate into epidermal lipids. A comparison between isolated epidermal cells and epidermal slices.

Suspensions of pig epidermal cells were prepared by trypsinisation of epidermis and incubated with I-14C-acetate in Eagle's minimum essential medium containing 10% serum. The incorporation of radioactivity into the total lipids of the cells increased with time despite the decrease in the proportion of viable cells which occurred during the period of incubation. The pattern of incorporation into the phospholipids and glycolipids showed similar changes with time to those observed previously with rat epidermal cell suspensions. Pig epidermal slices were incubated with I-14C-acetate in Eagle's minimum essential medium in the presence and absence of 10% serum. The proportion of radioactivity incorporated into the polar lipids was much greater in the epidermal slices than in the suspensions of epidermal cells. The pattern of incorporation in the phospholipids and glycolipids of epidermal slices differed from that found with epidermal cell suspensions and the pattern did not alter so markedly with the time of incubation. However, in each case reproducible patterns of incorporation were obtained under controlled conditions. The method of analysis can therefore be used to study lipid changes in small biopsies of normal and pathological skin.

Incorporation of I-14C-acetate into the lipids of isolated epidermal cells.

Suspensions of epidermal cells were prepared by trypsinization of rat epidermis and incubated with I-14C-acetate in Eagle's minimum essential medium. The incorporation of radioactivity into the total lipids of the cells was increased by the addition of serum to the medium. The pattern of incorporation into the main lipid classes was affected by the addition of serum to the medium and by alterations in the density of the cell suspensions. The incorporation of radioactivity into the total lipids increased approximately linearly over a 24-h period of incubation and the pattern of incorporation into the phospholipids and glycolipids altered with time. However, at each time interval studied, reporducible patterns of incorporation were obtained under controlled conditions. The incorporation of radioactive acetate therefore provides the basis for a very sensitive method of lipid analysis.

Phospholipase A and lysophospholipase activity of the epidermis.

Phospholipase A and lysophospholipase activities have been demonstrated in cow snout epidermis. The phospholipase A activity was dependent on Ca2+ ions and the pH for optimum activity was between 6-1 and 7-4.