Melano-macrophages in kidney and spleen of juvenile silverside (Odontesthes bonariensis): a structural, histochemical and enzymehistochemical study.

VIGLIANO, F.A.; BERMÚDEZ, R.; QUIROGA, M.I.; NIETO, J.M.

Foz do Iguaçu, Brasil/Puerto Iguazú, Argentina

Congreso; XV Pan American Congress of Anatomy; 2004

Pan American Association of Anatomy

Melano-macrophages (MMs) are pigmented phagocytic cells present in the parenchyma of haema-lymphopoietic organs of fish, which can aggregate forming structures named melano-macrophages centres (MMCs). This MMCs could participate in the remove of damaged cells among other functions. The aim of this study was to describe the structure and histochemical properties of MMCs present in the kidney and spleen of juveniles of Argentinian silverside in order to determine their function in this specie. Small pieces of kidney and spleen from fourteen healthy fish were dissected out. They were fixed in 10% calcium-formaldehyde and embedded in paraffin wax. On 1µm thick sections, hematoxilin-eosin, Gallego´s trichromic, Gomori method for reticulin, Perls’ Prussian blue for haemosiderin, Schmorl´s reaction for melanin, Aldehyde fuchsin technique for lipofuscin and enzymehistochemical assays for acid (ACP) and alkaline phosphatase (ALP) were performed. MMs were observed randomly distributed in the interrenal and splenic tissue, although their localization close to capillaries was frequent. They were oval-shaped with a large cytoplasm occupied by a yellowish to dark brown pigment. Within the kidney as wells as in the spleen, the MMs came together making up MMCs. They showed a variable shape and size, and were surrounded by a layer of flattened cells and collagen fibres with absence of reticular fibres. Melanin was detected in free MMs as well as in MMCs in both organs although a greater reactivity was observed in splenic MMCs. These centres also showed larger amount of haemosiderin. Moreover, the presence of lipofuscin inside these structures was constant. In relationship to enzyme activity, a negative reaction to ALP and strong positivity to ACP were observed. The presence of haemosiderin and lipofuscin inside MMCs, and their strong positivity to ACP could indicate their role in the phagocytosis of erythrocytes among another cells in agreement with previous reports in others teleost species.