Microradiographical determination of the dry mass density in the rat retina.

A method for the quantitative measurement of the dry mass density in retinal tissue is presented. Cryosections of rat retinas were freeze-dried and exposed to soft X-rays together with a reference system. The section thickness was measured optically. The X-ray energy absorbed by the retinal tissue was recorded photographically and the microradiographs were evaluated photometrically. These measurements were used to estimate the dry mass density for each retinal layer. Sources of variation were evaluated. The precision was found adequate. The present method allows a localized determination of the dry mass density and of the hydration in the retina at a microscopic resolution.