Quantitative assessment of a change of hemosiderin deposition with age in splenic compartments of rats.

Hemosiderin deposition was quantitatively estimated in paraffin sections stained using Perls' iron reaction in the spleens of untreated male rats aged from 0 to 28 months. Hemosiderin was deposited in the periarteriolar lymphocyte sheath (PALS), lymph follicles, and marginal zone, as well as in the red pulp which was the main compartment of hemosiderin deposition. Special attention was paid to the PALS and marginal zone. Marked hemosiderin deposition was evident from 4 months, although only few hemosiderin-laden macrophages appeared in the first 3 months. Hemosiderin deposition peaked at 12 months in the red pulp and at 20 months in the white pulp and marginal zone. The deposition in the white pulp and marginal zone was about 1/9 to 1/4 of that in the red pulp. A few hemosiderin-laden macrophages were found in the lymph follicles after 2 months. In the periarterial region of the splenic hilus, deposition of hemosiderin granules was observed even at 1 month when there was little hemosiderin deposition elsewhere. Since no arteries open there, the presence of hemosiderin-laden macrophages in the PALS and lymph follicles suggested movement of some macrophages from the red pulp and/or the marginal zone. In addition, hemosiderin deposition in the PALS increased with age after it decreased in the other compartments.