Abstract
During the course of an histochemical study of thermally injured rat skin, a unique differential staining property of heat-altered collagen was observed.
Methods. The abdomen of young adult male rats was exposed to various temperatures between 50°C and 80°C for 1-2 minutes in a thermostatically controlled water bath. The area exposed was limited by a shielding device. Immediately following the thermal exposure, skin blocks were excised which included both the exposed and shielded areas. These were immediately fixed in Carnoy's fixative to prevent solution of water soluble substances present as normal constituents of skin or as a result of the heat treatment.
Results. Paraffin sections (4 μ) were stained for 24 hours at room temperature by an aqueous solution of aniline blue (C.I. No. 707) and a mordant, phosphomolybdic acid. Both the normal and the heat-altered collagen of the rat skin stained an intense blue. When the hyperthermic episode ranged between 50 and 60°C, the heat-altered collagen was indistinguishable from that of normal unheated skin. At higher temperatures (70°C and 80°C) the heat-altered collagen showed a variable loss in structure, due to homogenization and swelling of the individual bundles. Orange G (C.I. No. 127) added to the above aqueous staining solution serves as a cytoplasmic and keratin stain.
When, however, the above stains (aniline blue, phosphomolybdic acid) were dissolved in absolute methanol and duplicate tissue sections stained for 24 hours, there was a striking difference in the staining properties of normal collagen and those of collagen which has been brought to temperatures of 70°C or above. In these circumstances, the thermally-altered collagen stained intensely with Orange G in contrast to the normal unheated collagen, which is still stained dark blue by the aniline blue.
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