Fluorescent staining of elastic tissue with Rhodamine B and related xanthene dyes

Summary Frozen sections, cut at 8 from various fresh tissues, were dried for 5 minutes over sulfuric acid, and then stained for 4 minutes in a 0.1% aqueous solution of Rhodamine B (Chroma) at pH 8.O. After soaking twice in butanol for 2 minutes each, the sections were kept on a warmer at 60° C for 2 minutes and then mounted in oil of cedar. Under ultraviolet microscopy, elastic fibers selectively stained yellow-orange against a pale blue background. No autofluorescence of elastic fibers was observed in guinea pig, rat, hamster or rabbit tissue in contrast to the autofluorescence of elastic fibers typically seen in human tissue.Similar fluorescent staining of the elastic tissue could be achieved by using a number of related xanthene dyes including pyronine, eosin B, acridine orange, pholoxin, phloxin B. More distantly related auranine O and thiazol yellow G were likewise used with success as fluorochromes for elastic fibers.Supported by a John A. Hartford Foundation Grant.