CONCERNING THE STAINING PROPERTIES OF ALDEHYDE BASIC FUCHSIN

Selective staining of the anterior pituitary of the frog and the rat is obtained using the solution of aldehyde basic fuchsin prepared from purified pararosaniline, or from some, but not all, commercially available basic fuchsin dyes. The results indicate that the active dye molecule is pararosaniline while rosaniline and magenta II, which may also be present in commercial samples of basic fuchsin, are inert. The selective staining of the pituitary is believed to be due to canboxyl groups in the tissue, which react with an intermediate, meta-stable species formed in the dye solution. The nature of this intermediate remains unknown, but its formation in the staining soloutions can be followed spectrophotometrically. On the basis of the spectral and staining data, the properties of the intermediate are discussed. There is no need of an oxidative step to obtain selective staining.