title: Inhibition by tunicamycin of mucin synthesis, not morphological changes, in epidermis during retinol-induced mucous metaplasia of chick embryonic cultured skin.
abstract: BACKGROUND
  Our previous studies have shown that epidermal mucous metaplasia of chick embryonic skin can be induced by culture in medium containing 20 microM retinol for only 8 hr and then in a chemically defined medium without retinol for 2 days and that retinol primarily affects the dermal cells, which then transform the epithelial cells into mucus-secreting cells.
  
  
  METHODS
  Tarsometatarsal skin of 13-day-old chick embryo was cultured with 20 microM retinol for 1 day and then without the vitamin but with 0.1 microgram/ml tunicamycin for 5 days. Effect of tunicamycin on epidermal mucous metaplasia was studied biochemically and morphologically.
  
  
  RESULTS
  Tunicamycin, which prevents the formation of N-glycans and inhibits maturation or morphological organization of various epithelial cells, irreversibly inhibited the synthesis of sulfated glycoproteins (O-glycans, mucin) in the epidermis only when applied to retinol-pretreated skin. Microvilli on the surface of the cells were well developed, but mucous granules surrounded by a limiting membrane were not observed in the upper cell layer of the epidermis, and many vesicles without electron-dense materials (mucin) and dilated rough endoplasmic reticulum were seen in the intermediate cell layers of the epidermis. When recombinants of 13-day-old normal epidermis and cultured dermis, which had been treated with retinol for 24 hr and with only tunicamycin for 2 days, were cultured without the antibiotic for 5 days, epidermal mucous metaplasia was induced.
  
  
  CONCLUSIONS
  These results suggest that tunicamycin did not prevent morphological changes induced by retinol but inhibited mucin synthesis by a direct action on the epidermis of retinol-pretreated skin. Because in some cell-line mucin precursors contain high mannose N-linked oligosaccharides side chains, tunicamycin may have inhibited mucin synthesis. Interaction between epidermal basal cells and retinol-pretreated dermal fibroblasts is prerequisite for epidermal mucous metaplasia. Thus, the present study suggests that N-linked protein glycosylation is not required for this interaction.
authors.affiliation: Department of Physiological Chemistry, Faculty of Pharmaceutical Sciences, Teikyo University, Kanagawa, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Obinata
authors.forename: Y
authors.initials: Y
authors.lastname: Akimoto
authors.forename: T
authors.initials: T
authors.lastname: Kawamata
authors.forename: S
authors.initials: S
authors.lastname: Shimizu
authors.forename: H
authors.initials: H
authors.lastname: Hirano
mesh_terms: D000818:Animals; D002642:Chick Embryo / Q000033:anatomy & histology / Q000378:metabolism; D003594:Cytoplasmic Granules / Q000378:metabolism; D004586:Electrophoresis; D004817:Epidermis / Q000187:drug effects / Q000196:embryology / Q000378:metabolism*; D006023:Glycoproteins / Q000037:antagonists & inhibitors; D006854:Hydrocortisone / Q000494:pharmacology; D007633:Keratins / Q000378:metabolism; D008679:Metaplasia; D009077:Mucins / Q000037:antagonists & inhibitors* / Q000096:biosynthesis; D009093:Mucus / Q000378:metabolism; D011506:Proteins / Q000378:metabolism; D012867:Skin / Q000196:embryology* / Q000378:metabolism / Q000473:pathology; D014415:Tunicamycin / Q000494:pharmacology*; D014801:Vitamin A / Q000494:pharmacology*
chemical_list: D006023:Glycoproteins; D009077:Mucins; D011506:Proteins; D014415:Tunicamycin; D014801:Vitamin A; D007633:Keratins; D006854:Hydrocortisone