Metanil Yellow - an Azo Dye Induced Histopathological and Ultrastructural Changes in Albino Rat (rattus Norvegicus)

Different azo dyes are widely used in textile, printing, cosmetic, drug and food processing industries. Metanil Yellow, a monosodium salt of 3-[[4-(Phenylamino) phenyl] azo] benzenesulfonic acid is one among those. It is a non-permitted food colour as well as an additive. Azo dyes are also used in laboratories as biological indicators or as pH indicators. There are varieties of food additives, constituting more than 25,000 items used as preservatives, dye or enhance food quality (Hirschbruch and Torres, 1998; Toledo, 1999). The great bulk of artificial colourings used in foods are synthetic food dye have been suspected of being toxic or carcinogenic and many have been banned whenever possible. Many authors (Reyes et al., 1996; Tanaka, 2005; Zraly et al., 2006) studied the metabolic and toxicological disorders induced by the administration of specific food colourant additives to rats and other mammals. Many azo compounds are genotoxic in short-term tests and carcinogenic in laboratory animals (Combes and Haveland-Smith, 1982; Sasaki et al., 2002). The safety of common red colour amaranth is currently being reinvestigated in view of its suggested carcinogenic and teratogenic effects (Larson, 1975; Holmberg, 1978). In 2001, Tsuda et al., reported that amaranth and allura red induce colon DNA damage at a very low dose in mice. The study of the carcinogenic and mutagenic effects of tartrazine are established by some authors which gives variable results (Jones et al., 1964; Patterson and Butler, 1982; Maekawa et al., 1987; Borzelleca and Hallagan, 1988; Collins et al., 1990; Collins et al., 1992; Reyes et al., 1996; Koutsogeorgopoulou et al., 1998; Walton et al., 1999; Sasaki et al., 2002). Epidemiological studies of food colour additives are difficult, because exposure cannot be accurately assessed. Thus, risk assessment largely depends on laboratory toxicity studies. Allura red produces evidence of both physical and behavioural toxicity in developing rats (Vorhees et al., 1983). Poceau 4R (new Coccine) which is permitted as a food colour in the U.S.; but it is neither mutagenic in Salmonella (Fujita and Sasaki, 1993), nor teratogenic in mice (Larson, 1975). It is studied that mammalian azoreductase in the intestinal wall or liver reduced the azo dye to free aromatic amines (Chung and Cerniglia, 1992; Chung et al., 1992; Prival et al., 1988). Oral administration of Metanil Yellow at 3% (w/w) dose level to adult male albino rats resulted in a remarkable decrease in food intake and body weight gain in both normal protein (NP) and low protein (LP) groups (Singh 1996). Chronic consumption of Metanil Yellow by developing and adult rats affected the brain regional levels (Nagaraja and Desiraju,1993). Metanil Yellow (MY) and Malachite green (MG) have promoted effects on the development of hepatic preneoplastic lesions (Gupta et al., 2002). Metanil Yellow has been found to cause testicular damage in gametogenic elements to arrest spermatogenesis in guinea pigs, rats and mice (Khanna and Das, 1991) and to cause alteration in haemopoietic system in rats (Mehrotra et al., 1974). Reduction products of azo compounds possess toxic and mutagenic properties (Chung, 1983). Although the basic ABSTRACT The azo dye Metanil Yellow is used in different food items for dyeing and colouring purposes. The chronic exposure of this non-permitted food colour as well as additive in albino rat (Rattus norvegicus) for 30 days at a dose of 3.0g/kg body weight was invested through histopathological and ultrastructural changes in stomach, intestine, liver and kidney. Several changes were found under histopathological as well as ultrastructural observations. Histopathological lesions as observed in stomach were disruption of gastric folds, profuse secretion of mucus, necrosis in columnar epithelial cells and gastric glands. In intestine, the villi were damaged severely. The absorptive columnar epithelial cells were totally damaged in some regions, brush border and lamina propria were disrupted due to toxicity. Histopathological lesions were also observed in the liver and kidney of albino rats. In liver, there was an extensive degeneration of hepatocytes, diminish in cytoplasmic content. Appearance of pycnosis of nuclei and damage occurred in the central vein regions. In kidney, necrosis of tubular epithelium, cloudy swelling of epithelial cells of renal tubules and disruption in Bowman’s capsule were also prominent features of toxicosis. Under ultramicroscopic observations lesions were found in the mucosal folds and columnar epithelial cells of stomach and intestine. Several changes were also shown in the absorptive columnar epithelial cells as well as in the microvilli of intestine. All these alterations marked the toxic effects of Metanil Yellow in rat.