Abstract
Variation of the ratio of pyridine to neutral solvent (tetrahydrofurane, isooctane or xylene) was employed to investigate the reaction of phosphoryl chloride (POCl3) with tissue components. Two types of products appear to be formed, one (phosphoric acids and (?) amides) reacting with toluidine blue, and another combining with leukofuchsin. Formation of the latter is in general enhanced by the presence of base (pyridine) in the phosphorylation mixture, while that of the former is not. In vitro, compounds with both the =POCl and ≡PO groups react with leukofuchsin in the presence of pyridine, suggesting that a substrate-phosphate-pyridine complex is in part responsible for the direct Schiff reaction after phosphorylation. Despite the wide distribution of reactive substrates, under appropriate conditions selective staining of certain tissue components, e.g., cardiac "colloid," can be obtained.