The effect of all-trans-retinoic acid on the synthesis of epidermal cell-surface-associated carbohydrates

Abstract

All-trans-Retinoic acid at concentrations > 10-7 M stimulated the incorporation of D-[3H]glucosamine into 8 M-urea/5% (wt/vol) sodium dodecyl sulphate extracts of 1 M-CaCl2-separated epidermis from pig ear skin slices cultured for 18 h. The incorporation of 35SO42-, L-[14C]fucose and U-14C-labeled L-amino acids was not significanlty affected. Electrophoresis of the solubilized epidermis showed increased incorporation of D-[3H]glucosamine into a high MW glycosaminoglycan-containing peak when skin slices were cultured in the presence of 10-5 M-all-trans-retinoic acid. The labeling of other epidermal components with D-[3H]glucosamine, 35SO42-, L[14C]fucose and U-14C-labeled L-amino acids was not significantly affected by 10-5 M-all-trans-retinoic acid. Trypsinization dispersed the epidermal cells and released 75-85% of the total D-[3H]glucosamine-labeled material in the glycosaminoglycan peak. Most of this material was extracellular in control and 10-5 M-all-trans-retinoic acid-treated epidermis. Increased labeling of extracellular epidermal glycosaminoglycans was observed when human skin slice were treated with all-trans-retinoic acid, indicating a similar mechanism in both tissues. Increased labeling was found when the epidermis was cultured in the absence of the dermis, suggesting a direct effect of all-trans-retinoic acid on the epidermis. Increased incorporation of D-[3H]-glucosamine into extracellular epidermal glycosaminoglycans in 10-5 M-all-trans-retinoic acid-treated skin slices was apparent after 4-8 h in culture and continued up to 48 h. all-trans-Retinoic acid (10-5M) did not affect the rate of degradation of this material in cultures chased with 5 mM-unlabeled glucosamine after 4 or 18 h. Cellulose acetate electrophoresis at pH 7.2 revealed that hyaluronic acid was the major labeled glycosaminoglycan (80-90%) in both control and 10-5 M all-trans-retinoic acid-treated epidermis. The labeling of epidermal plasma membranes isolated from D-[3H]glucosamine-labeled skin slices by sucrose density gradient centrifugation was similar in control and 10-5 M-all-trans-retinoic acid-treated tissue. Increased synthesis of mainly extracellular glycosaminoglycans (largely hyaluronic acid) may be the 1st response of the epidermis to excess all-trans-retinoic acid. [Vitamin A plays an important role in epithelial differentiation.].