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Abstract
The distribution of protein down to a subcellular level was determined in the normal lens of the rat at different ages by means of a quantitative microradiographical technique. In the peripheral cortex, the protein content remained almost constant throughout life. The mean protein concentration in this region of the lens was 0.30 Gm.-cm-3, with a variation within the lens fibers of about ± 0.04 Gm.-cm-3. The amount of protein was found to increase toward the center of the lens in all rats except the newborn. In the center of the nucleus from old lenses, protein concentrations as high as 0.90 Gm.-cm-3 were recorded. Here, the variation in dry weight within the lens fibers was very small. The protein concentrations were converted to percentages by volume, the highest values being found to exceed 65 per cent by volume. The distribution of protein is discussed in relation to the optical properties of the lens, the refractive index being calculated from the protein content. The calculated indices showed good agreement with refractometric determinations in isolated parts of lenses. It was concluded that, in normal transparent lenses, the changes in refractive index were always regular and continuous, except for the moderate intracellular variations.