TETRAZOLIUM STUDIES ON THE RETINA: I. INTRODUCTION AND TECHNIQUE

The retina has physical dimensions that make it especially favorable for incubation studies in its unsectioned state. With blue tetrazolium anti suitable substrates, dehydrogenase activity is demonstrated in various, but characteristic, forms and places. A red color that depends on enzymatic activity is found in the reticular layers, nerve fiber layer, and lipid portions of the retina. This appears to represent a solubilization of reduced and partially reduced formazan in the lipid portions of the retina. The blue precipitate is found in mitochondria-like granules within certain cells, notably in the ellipsoids of the rods and cones, glial cells, Müller's cells, and to some extent in ganglion cells. It is also found as amorphous and rod-like crystalline deposits in the inner layers of the retina and as a fine dust-like deposit in the nerve fiber layer. Metabolic activity in the retina as reflected by tetrazolium precipitation persists for hours after death and is present about equally in peripheral and central regions of the retina. The reduction brought about by the utilization of specific substrates representing intermediates in the major metabolic pathways will be the subject of subsequent papers of this series.