The effect of light on the quantity of phagosomes in the pigment epithelium

Abstract

The effect of light on the number of phagosomes within the pigment epithelium was studied using Rana pipiens tadpoles dark-adapted for various intervals before light stimulation. Two populations of phagosomes were observed. One consists of large packets of rod outer segment discs 4–10 μm long and 5 μm wide. Light stimulation following various periods of darkness results in a steady increase in the density of these large phagosomes reaching a peak 2–3·5 times above control levels after 2 hr of light. The maximum number of large phagosomes was obtained in animals dark adapted for 3 days before light stimulation. The second population of phagosomes consists of small packets of outer segment discs 1–2 μm in diameter. The number of these phagosomes does not change with different conditions of illumination. Electron microscopic analysis indicates that the small phagosomes are lost from the rod outer segment tips as small whorls of 5–30 discs.