A new fluorescent method for the demonstration of macromolecular aldehydes.

The fluorochrome, p-hydrazinoacridine (HA), is used to stain selectively natural macromolecular aldehydes as occur in elastic tissue as well as periodic acid (oxidized) or hydrochloric acid (hydrolyzed) engendered polyaldehydes (e.g., respectively of glycogen, mucosubstances and deoxyribonucleic acid). The reaction is independent of SO2 required in Schiff-type reactions. The mechanism of the staining reaction is presumably via the formation of fluorescent hydrazones from aldehyde condensation with HA. Aldehyde blocking agents, i.e., thiosemicarbazide and sodium borohydride, block the staining reactions with HA. In view of the controversy surrounding the mechanism of Schiff-type reactions and the lack of an adequate explanation for the affinity of miscellaneous fluorochromes for elastic tissue, p-hydrazinoacridine appears to be an ideal reagent, combining a simple staining procedure, excellent histological results and a straightforward mechanism for its selectivity.