The portions of cytoplasm that have many ribosomes stain in purple-blue by hematoxylin. It has already been mentioned that the affinity of acidic structures for basic dyes is called basophilia and these regions of the cytoplasm are called basophilic.
A very demonstrative example of cytoplasmic basophilia can be seen in the exocrine secretory cells of the pancreas, also called acinar cells of the pancreas. These are the cells that secrete pancreatic juice, which is rich in proteins.
The general shape of these cells is pyramidal or pear-shaped and they are grouped in small spherical clusters called acini (more details about these glands in the chapters “Glandular Epithelia” and “Pancreas”). The center of the image shows one acinus, surrounded by portions of neighbour acini.
The region of cytoplasm that forms the base of each pyramidal acinar cell contains a large concentration of RNA packed in ribosomes, besides proteins. For this reason this area stains with both hematoxylin and eosin, furnishing a purple color.
As you move the mouse or click on the figure, two exocrine cells of an acinus appear delimited by dark lines.
The basophilic portion of their cytoplasm will appear in light blue. A few nuclei of acinar cells will appear shaded in a darker tone of blue.
The region at the higher part of the pyramidal cell, also called “apical region”, is filled with secretory grains, which contain a high concentration of proteins of the pancreatic juice. They are preferentially stained in pink-orange by acidic dyes such as eosin. This region is therefore acidophilic (or eosinohilic) and will appear pink after you place the mouse or click on the image.
Take the opportunity to observe that these secretory cells have very large and prominent nucleoli, highlighted in some of the nuclei.
Pancreas. Hematoxylin and eosin. Medium magnification.
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