5. OVERVIEW ON ENDOGENOUS PIGMENTATION IN DOMESTIC ANIMALS by G. D. DESAI 1, M. M. CHUDASAMA2, S. V. DAMOR3,

Abstract

Pigments are colored substances, some of which are normal constituents of cells (melanin), while others are abnormal and collect in cells under special circumstances. Pigments are usually classified broadly into two groups: exogenous (formed outside the body) and endogenous (formed inside the body). Lipofuscin is an insoluble pigment within cells formed during aging or atrophy. Microscopically, lipofuscin pigment appears as minute yellow-brown granules. Grossly, the lipofuscin pigment may impart a brownish discoloration to tissues when present in sufficient amounts (brown atrophy). Lipofusin is especially prominent in the brain neurons, myocardial cells and in the adrenal and thyroid glands. Melanin is a normal endogenous brown-black pigment which provides color to the skin, hair, leptomeninges and choroid of the eyes. Melanin is a high molecular weight biochrome bound to protein and it is a synthesized by melanocytes. In domestic mammals, function of melanin is protection against solar ultraviolet radiation.
Hemosiderin pigment represents aggregates of ferritin micelles. Heart failure cells are hemosiderin laden alveolar macrophages that occur subsequent to chronic left heart failure and passive congestion of the lungs. Bilirubin is an orange-yellow pigment derived primarily from the breakdown of hemoglobin. Bilirubin is formed by reticulo-endothelial cells any place in the body, but especially in the spleen. Icterus is the condition in which tissues are stained (yellowish) with either non-conjugated or conjugated bilirubin. It implies hyperbilirubinemia. Grossly, the yellowish discoloration is best observed in the sclera or other tissues which are pale normally. Icterus is classified based on the causative mechanism : Hemolytic icterus (prehepatic), toxic icterus (hepatic) and obstructive icterus (posthepatic).
KEY WORD: Endogenous pigments, lipofuscin, Bilirubin, Haemolytic icterus.