Spleen and Liver Pigmented Macrophages of Rana Esculenta L. A New Melanogenic System?

Abstract

The present study reports the results of a morpho-functional analysis of spleen pigmented cells from Rana esculenta L. and comparison with liver melanin-synthesizing cells, belonging to the macrophage cell lineage. Cytological and cytochemical analyses show that parenchymal pigmented cells of the spleen, like those of the liver, are positive to peroxidase and lipase reactions and have phagocytic properties. The observation of premelanosomes in various stages of differentiation, together with the demonstration of dopa oxidase activity in the melanosome proteins, indicate that spleen pigmented macrophages have endogenous melanogenic ability as do liver pigmented macrophages. Attempts to demonstrate tyrosinehydroxylase activity in melanosome protein extracts from frog spleen and liver, using the same protocol as for mammalian tyrosinases, gave negative results. As regards the dopa oxidase activity revealed, some of its properties differ from the typical behaviour observed for tyrosinases from different sources. Peroxidase activity is shown in spleen and liver melanosome proteins with p-phenylenediamine-pyrocatechol (PPD-PC), and not with typical peroxidase substrates. Suitable inhibition tests revealed that dopa oxidase and peroxidase activities might be supported by two different proteins. Liver melanosome extracts display a very strong laccase (dimethoxyphenoloxidase) activity but spleen extracts do not. Differences observed in the enzymatic properties of the spleen and liver melanosomes suggest that pigmented macrophages may undergo tissue-specific differentiation. These preliminary data show that the melanin pathway of pigmented macrophages is different from that of melanocytes and may pave the way to identification of a new melanogenic pathway in vertebrates.

Internal pigment cells respond to external UV radiation in frogs

“…Melanomacrophages are rounded (Sichel et al, 1997) and contain the catabolic substances hemosiderin and lipofuscin (Agius, 1981;Agius and Roberts, 2003). Both types of internal pigment cells have cytoprotective functions against free radicals (Mcgraw, 2005), produce melanin (Gallone et al, 2002(Gallone et al, , 2007 and detoxify pollutants (Fenoglio et al, 2005) in addition to functions related to the immune system (Franco-Belussi et al, 2013) and pathologies (Roberts, 1975). There is evidence that melanin participates in innate immunity and regulates cytokine activity (Mackintosh, 2001).…”

“…Fish and amphibians have pigmented cells called visceral melanocytes and melanomacrophages in internal organs and membranes (Gallone et al, 2002;Franco-Belussi et al, 2011Nilsson Sköld et al, 2013). Visceral melanocytes are in many ways similar to skin melanocytes (Zuasti et al, 1998).…”

Comparative Histological Study of Parenchymal Arrangements in Three Orders of Reptilian Livers

“…Aggregations of pigmented cells, termed MMs, have been found in the livers of some fishes [8,9], amphibians [10][11][12][13], and reptiles [14][15][16][17]. Previous studies demonstrated that the pigmented cells of amphibian livers are cells belonging to the macrophage lineage of Kupffer cells [23][24][25] as well as the MMs centers of fishes [19,26,27].…”

“…In heterothermic vertebrates, aggregations of pigmented cells termed melanomacrophages (MMs) have been identified in the livers of some fishes [8,9], amphibians [10][11][12][13], and reptiles [14][15][16][17]. Extracutaneous melanin-containing cells have been detected in various tissues and organs such as the liver, spleen, kidney, and lungs [9,18,19].…”

Pigmentation in Anuran Testes: Anatomical Pattern and Variation

“…Ectothermic vertebrates have a well-developed system of melanin-containing cells, distributed among several organs (liver, spleen, lung, heart, thymus, and gonads) and tissues (meninges and connective tissues surrounding blood vessels) composing an extracutaneous pigmentary system (Gallone et al, 2002).…”