A microfluorometric study of masked metachromasia in cells of the endocrine polypeptide (APUD) series

Synopsis Masked metachromasia can be demonstrated by staining with a metachromatic basis dye after a Feulgen-type hydrolysis of suitably fixed tissue, and is believed to be indicative of polypeptides with a high concentration of side-chain acidic groups and a random-coil conformation. In this investigation, the metachromatic fluorochrome Coriphosphine O was used. After staining, the degree of metachromasia under various conditions and in several tissues was assessed by microspectrofluorometric measurements of the ratio of metachromatic fluorescence (red) to orthochromatic fluorescence (green). This technique was employed, in the first instance, to determine the optimum staining conditions; details of the final staining method are presented. Measurements of metachromasia in different tissues under standardized conditions showed that the degree of metachromasia varied between different cell types in the APUD series.