The dermis is required for the synthesis of extracellular glycosaminoglycans in cultured pig epidermis.

1. Slices of pig ear skin were cultured in the presence of D-[3H]glucosamine and the epidermis solubilised in 8 M urea/5% sodium dodecyl sulphate was analysed by polyacrylamide gel electrophoresis. A high molecular weight peak, previously shown to contain glycosaminoglycans, was a major labelled component of epidermis separated from dermis using either CaCl2, dispase or trypsin. This material was unlikely to represent dermal contamination of the epidermis since (a) it was present mainly in epidermis rather than dermis, and (b) both histology and comparison of protein compositions showed the epidermis to be essentially free of dermal components. 2. When the epidermis was separated from dermis before rather than after culture (using CaCl2, dispase, trypsin or suction) the labelled glycosaminoglycan peak was never observed. The labelling of other epidermal glycoconjugates was unaffected. Thus the dermis was necessary specifically for the synthesis of epidermal glycosaminoglycans. 3. All-trans-retinoic acid (1 x 10(-5) M) had a marked effect on the labelling of the epidermal but not the dermal glycosaminoglycan peak, indicating that the epidermal glycosaminoglycans were not synthesised in the dermis. 4. The results suggest that dermal influences in the epidermis could be mediated via dermal control of epidermal glycosaminoglycan synthesis.