The -SH and SS positive components in dermal connective tissues: a study by N-(7-dimethylamino-4-methyl-3-coumarinyl) maleimide (DACM) stain.

Although -SH and SS positive components in dermal connective tissue have been observed by N-(7-dimethylamino-4-methyl-3-coumarinyl) maleimide (DACM) stain, their nature is as yet unknown. In our study, we stained several organs such as human skin, rabbit aorta, auricle, and trachea using DACM stain, and studied the distribution of -SH groups and SS linkages among the elastic fibers in those organs. In the dermis of human skin, a moderately strong fluorescence by both -SH and SS stain was present all over the layer, especially in the lower half among collagen fibers in a fine linear or wavy pattern, and a fluorescence ascending vertically from the lower papillary dermis toward the epidermis was also observed. In rabbit aorta, a strong fluorescence by both -SH and SS stain was observed on well-developed elastic fibers. In the matrix of rabbit elastic cartilage, a strong reticular fluorescence by both -SH and SS stain was present. On the other hand, in rabbit hyaline cartilage, no -SH fluorescence was present on any components of the cartilage. However, though a diffuse moderate fluorescence for SS linkages was observed in the matrix, there was no reticular fluorescence such as that seen in the elastic cartilage. These results suggest that the -SH and SS components observed in the dermis by DACM stain are in fact elastic fibers, more precisely, "elastic tissue microfibrils".