The interphotoreceptor space: II. Histochemistry of the matrix

Abstract

Five histochemical techniques, ruthenium red, Alcian blue, colloidal iron, phosphotungstic acid and silver methenamine, were used to demonstrate at the ultrastructural level the interphotoreceptor matrix of immature and adult mice and rats. The cell coat of all the cells delimiting the interphotoreceptor space was the first and only demonstrable component in the space in the undifferentiated newborn retina. This component continues to be significant throughout life. The possibility that sloughing of cell coat occurs and that it constitutes the sialoglycan component of isolated matrix ( Berman and Bach, 1968) is discussed. Stained particles in the pigment epithelium (PE) were identified as various forms of melanosomes and lysosomes that probably have no precursor relationship with similarly stained substances in the interphotoreceptor space. A few other small vesicles in the Golgi region and apical cytoplasm of immature and adult PE and immature photoreceptors may carry cell coat or other matrix constituents to the cell surface. Chondroitin sulfate and hyaluronic acid, the other known components of the matrix, may be lost during preparative procedures. Alternatively, these macromolecules may be loosely bound to the cell coat; their distribution, therefore, may be reflected by these histochemical stains.