Some aspects of the value of Sudan Black B in lipid histochemistry

The lipid dye Sudan Black B, as generally used to demonstrate lipids in the interior of the cell nucleus, was studied with regard to its staining properties for isolated nuclei in relation with its chromatographic characteristics in solution, as well as with a model system consisting of lipid containing polyacrylamide films. Isolated nuclei are stained with Sudan Black B dissolved in ethylalcohol, only when the dye-solution is at least one month old. Extraction with chloroform-methanol (2:1) before staining resulted in a decrease of 35% in intensity. Treatment with proteolytic enzymes and DNA-se caused a complete disappearance of the staining capacity. The binding of Sudan Black B with phospholipids enclosed in the form of liposomes in modelfilms when stained with this dye in ethylene glycol obeys the law of Lamber-Beer, Proteins were however, also coloured by the dye. The chromatographic experiments showed that the dye is built up from two main and a number of secondary products. The secondary products which increase by aging of the dye-solution, change the spectrophotometric properties of the total dye and show a specific binding. The conclusion was reached that on the basis of a positive reaction with Sudan Black B no definite conclusions can be drawn about the presence of lipids in the interior of the cell nucleus.