The fluroescent profiles of keratohyalin granules of newborn rat epidermis with a new fluorescent thiol reagent (DACM).

A highly specific fluorescent thiol reagent, N-(7-Dimethylamino-4-methyl-coumarinyl)maleimide (DACM) has been used to examine the newborn rat skin in order to elucidate the cystine-rich keratohyalin granules or dense homogeneous deposits. After reduction of the disulphide bond with 2-mercaptoethanol, the periphery of the stratum corneum cells showed a very distinct fluorescence and the cytoplasm of the stratum corneum, granulosum and spinulosum showed moderate fluorescence. No fluorescence was observed, however, over the keratohyalin granules themselves. Intense, spotty fluorescence was observed from the remnants of nuclei and at the periphery of large keratohyalin granules of the stratum granulosum cells, which were assumed to be dense homogeneous deposts according to their distribution pattern. As the intense fluorescence elicited with DACM determines the abundance of cystine content in the material, cystine was found to be very scarce in keratohyalin granules, but abundant in dense homogeneous deposits and at the periphery of the stratum corneum cells.