Squamous Metaplasia of the Tracheal Epithelium in Organ Culture. II. Nutritional Influences 1

Abstract

Summary

The mucociliary epithelium of the adult hamster trachea undergoes squamous metaplasia in organ culture when maintained in a complex, chemically-defined medium (Waymouth's MAB 87/3) without serum. This change fails to develop in explants cultured in Eagle's minimum essential medium (MEM) (8, 9). To determine the factors promoting squamous metaplasia, nutritional constituents in Waymouth's MAB 87/3 medium but not present in MEM were divided into five groups: (a) insulin and glutathione, (b) vitamins C, B₁₂ and biotin, (c) nucleic acid intermediates, d) inorganic salts and e) nonessential amino acids. Test media were formulated by adding each group or combinations of groups to Eagle's MEM. Organ cultures were maintained in the test media for 4 weeks and then examined histologically. The nonessential amino acids were most important in enhancing metaplasia and keratinization. When nonessential amino acids were added individually to MEM, L-glutamic acid and L-serine seemed most influential in inducing metaplastic changes.