Chemical basis for the histological use of safranin o in the study of articular cartilage

Abstract

Interpretation of the histological behavior of metachromatic dyes requires information regarding their absorption spectra in solution and in histological sections. Safranin 'O' is a cationic dye, which under certain circumstances exhibits metachromasia. In dehydrated cartilage sections stained with safranin 'O' it is in the orthochromatic form. In such a form it is bound to the tissue glycosaminoglycan stoichometrically. This stoichometric binding infers that safranin 'O' may be used to quantitate the amount of proteoglycan present in cartilage [ 1[. In a number of disease states, cartilage degradation is accompanied by changes in distribution or amount of glycosaminoglycan in the tissue. Under such circumstances, cationic dyes such as safranin 'O' and toluidine blue 'O' have been used to assess the amount of proteoglycan present in diseased tissue [ 1 , 2[.