[Histologic demonstration of adrenal macrophages as a member of mononuclear phagocytic system in guinea pig models].

Macrophages as mononuclear phagocytes, function in removing foreign substances and in the initiation of the immune response. Although some tissue-specific macrophages such as Kupffer's cells and alveolar macrophages are well-known, any knowledge about the adrenal macrophages are not yet documented in the textbooks. The aim of this study was to demonstrate the resident macrophages in the adrenals of a total 16 (8 pregnant, 8 non-pregnant) guinea pigs. Four of the animals were injected with India ink (no intervention for the other animals), and after sacrificing all animals, removed adrenals were fixed in Bouin's solution, and embedded in paraffin. Sections were stained with haematoxylin-eosin (HE) and periodic acid-Schiff (PAS) methods. Many macrophages with yellowish-brown cytoplasm in HE slides, especially adjacent to sinusoids, were observed primarily in the zona reticularis, suggesting that they are rich in lipofuscin pigment. These cells were also PAS positive. Adrenals of India ink-injected animals demonstrated perisinusoidal macrophages phagocytosing the ink. Much more adrenal macrophages were seen in the pregnant animals in comparison with the non-pregnants. It has been previously reported that the number of human macrophages increases with rising concentrations of estrogen during pregnancy. Thus, higher number of adrenal macrophages in pregnant animals was an expected result. Since they secrete cytokines, macrophages are favorable cells in terms of interactions of the neuro-endocrine organs with the immune system. Some cytokines released by macrophages have been stated to induce adrenocortical steroidogenesis independent from adrenocorticotropic hormone through medullary catecholamines. Thus, macrophages may have a significant role in the immune-adrenocortical communications within the adrenal. Finally, resident macrophages of the adrenals wait to be documented in the textbooks.