Light and electron microscopic observation of specific atrial granules using water-miscible resin as an embedding medium.

A mixture of glycol methacrylate (GMA) and Quetol 523 was examined as an embedding medium for atrial tissue to be selectively stained for specific atrial granules. Semi-thin sections of rat atrial tissue embedded in this resin were stained with lead hematoxylin and observed under a light microscope. Atrial granules were found to be specifically stained blue black with lead hematoxylin. The same semithin sections stained with OsO4 vapor were examined electron microscopically and the atrial granules could be distinguised clearly from other cytoplasmic components. The GMA-Quetol 523 mixture is a useful embedding medium for studying the distribution of specific atrial granules by light and electron microscopy.