Primary inducible fluorescence in secretory granules of tumor cells supravitally stained by a toluidine blue dye.

In a toluidine blue dye (British Drug Houses, batch no. 651880), we report a purple chromato­ graphic fraction (Rf—0,55) with a spectral absorption peak at 622 m/u, which has the property to induce immediate bright yellow fluorescence (primary inducible fluorescence) in cytoplasmic gra­ nules of tumor cells. The cells are unfixed, supravital stained and examined by fluorescence micro­ scopy. The mean number of fluorescent granules per tumor cell was 36, ranging from 19 to 64 (50 cells). The effect of ultraviolet illumination on cells with fluorescent reaction is described, with reference to the shift of colour emission in the cytoplasmic bodies. These granules are Sudan Black and Oil Red positive, and become black after fixed cells are treated by osmium tetroxid. Actively growing cells accumulate basic dyes in lysosomes, and on this evidence, we base our belief that the granules of tumor cells with positive fluorescent reaction to this toluidine blue contain lipids, probably un­ saturated fatty acids, are of secretory nature and m ight be derived from primary lysosomes.