Ajay K. Chatterjee

Differential response of cellular antioxidant mechanism of liver and kidney to arsenic exposure and its relation to dietary protein deficiency

The effect on antioxidant defense system of liver and kidney of sub-acute i.p. exposure to sodium arsenite (3.33 mg/kg b.w. per day) for 14 days was studied in male Wistar rats fed on an adequate (18%) or a low (6%) protein diet. Following arsenic treatment, liver showed significantly enhanced concentration of glutathione and increased activities of glutathione reductase and glutathione-S-transferase on either of the dietary protein levels. Liver glutathione peroxidase and glucose-6-phosphate dehydrogenase activities increased significantly on an adequate protein diet while glutathione peroxidase activity decreased significantly on a low-protein diet. Lipid peroxidation and superoxide dismutase activity of liver remained unaltered on either of the dietary protein levels. On the other hand, kidney of arsenic-treated rats receiving either of the dietary protein levels showed significantly increased lipid peroxidation and decreased superoxide dismutase and catalase activities. Kidney glutathione content and glutathione reductase activity remained unaltered while glutathione peroxidase activity increased and glutathione-S-transferase activity decreased significantly on a low-protein diet following exposure to arsenic. On an adequate protein diet glucose-6-phosphate dehydrogenase activity in kidney, however, became significantly elevated following arsenic treatment. In Wistar rats, after 14 days of treatment with 3.33 mg As/kg b.w. i.p. the kidney seemed to be more sensitive to arsenic, and liver appears to be protected more by some of the antioxidant components, such as, glutathione, glutathione-S-transferase and glucose-6-phosphate dehydrogenase. It appears that low-protein diet influences the response of some of the cellular protective components against arsenic insult but does not lead to unique findings.

Possible Beneficial Effects of Melatonin Supplementation on Arsenic-Induced Oxidative Stress in Wistar Rats

The effects of melatonin on arsenic-induced changes on cellular antioxidant system were studied in male rats of the Wistar strain. Arsenic treatment (i.p. as sodium arsenite) was done at a dose of 5.55 mg/kg body weight (equivalent to 35% of LD50) per day for a period of 30 days, while melatonin supplementation (i.p.) was performed at a dose of 10 mg/kg body weight per day for the last 5 days prior to sacrifice. Melatonin supplementation reversed the arsenic-mediated changes in reduced glutathione (GSH) level and lipid peroxidation in liver and kidney. Arsenic-induced decreased glutathione reductase activity in liver and increased activity in kidney was appreciably counteracted by melatonin. Melatonin also inhibited arsenic-induced free hydroxyl radical production in the tissues. The decreased superoxide dismutase (SOD) activity in liver and kidney and that of catalase in liver due to arsenic treatment were also counteracted by melatonin. It is suggested that melatonin acts as a protective agent against arsenic-induced cellular oxidative stress.

Protective Effect of N‐Acetylcysteine Against Arsenic‐Induced Depletion In Vivo of Carbohydrate

N‐acetylcysteine (NAC), a synthetic aminothiol, possesses antioxidative and cytoprotective properties. The present study evaluates the effect of NAC supplementation on arsenic‐induced depletion in vivo of carbohydrates. Arsenic (as sodium arsenite) treatment (i.p.) of male Wistar rats (120–140 g b.w.) at a dose of 5.55 mg/kg body weight (35% of LD50) per day for a period of 30 days produced a significant decrease in blood glucose level (hypoglycemia) and a fall in liver glycogen and pyruvic acid contents. The free amino acid nitrogen content of liver increased while that of kidney decreased after arsenic treatment. Arsenic also enhanced the liver lactate dehydrogenase activity whereas glucose 6‐phosphatase activity in both liver and kidney decreased significantly following arsenic treatment. Transaminase activities in liver and kidney were not significantly altered except the glutamate–pyruvate transaminase activity that was reduced in kidney after arsenic treatment. Oral administration of NAC (163.2 mg/kg/day) for last 7 days of treatment prevented the arsenic‐induced hypoglycemia and glycogenolytic effects to an appreciable extent. There was also recovery of liver pyruvic acid as well as liver and kidney free amino acid nitrogen content after NAC supplementation. Arsenic‐induced alteration of glucose 6‐phosphatase activity in both liver and kidney was also counteracted by NAC. It is suggested that carbohydrate depletion in vivo due to exposure to arsenic can be counteracted by NAC supplementation.

Dietary protein restriction causes modification in aluminum-induced alteration in glutamate and GABA system of rat brain

BackgroundAlteration of glutamate and γ-aminobutyrate system have been reported to be associated with neurodegenerative disorders and have been postulated to be involved in aluminum-induced neurotoxicity as well. Aluminum, an well known and commonly exposed neurotoxin, was found to alter glutamate and γ-aminobutyrate levels as well as activities of associated enzymes with regional specificity. Protein malnutrition also reported to alter glutamate level and some of its metabolic enzymes. Thus the region-wise study of levels of brain glutamate and γ-aminobutyrate system in protein adequacy and inadequacy may be worthwhile to understand the mechanism of aluminum-induced neurotoxicity.ResultsProtein restriction does not have any significant impact on regional aluminum and γ-aminobutyrate contents of rat brain. Significant interaction of dietary protein restriction and aluminum intoxication to alter regional brain glutamate level was observed in the tested brain regions except cerebellum. Alteration in glutamate α-decarboxylase and γ-aminobutyrate transaminase activities were found to be significantly influenced by interaction of aluminum intoxication and dietary protein restriction in all the tested brain regions. In case of regional brain succinic semialdehyde content, this interaction was significant only in cerebrum and thalamic area.ConclusionThe alterations of regional brain glutamate and γ-aminobutyrate levels by aluminum are region specific as well as dependent on dietary protein intake. The impact of aluminum exposure on the metabolism of these amino acid neurotransmitters are also influenced by dietary protein level. Thus, modification of dietary protein level or manipulation of the brain amino acid homeostasis by any other means may be an useful tool to find out a path to restrict amino acid neurotransmitter alterations in aluminum-associated neurodisorders.

Response of regional brain glutamate transaminases of rat to aluminum in protein malnutrition.

BackgroundThe mechanism of aluminum-induced neurotoxicity is not clear. The involvement of glutamate in the aluminium-induced neurocomplications has been suggested. Brain glutamate levels also found to be altered in protein malnutrition. Alterations in glutamate levels as well as glutamate-α-decarboxylase in different regions of rat brain has been reported in response to aluminum exposure. Thus the study of glutamate metabolising enzymes in different brain regions of rats maintained on either normal or restricted protein diet may be of importance for understanding the neurotoxicity properties of aluminium.ResultsDietary protein restrictions does not have an significant impact on regional aluminum content of the brain. The interaction of aluminum intoxication and protein restriction is significant in the thalamic area and the midbrain-hippocampal region in cases of glutamate oxaloacetate transaminase. In the case of gluatmate pyruvate transaminase, this interaction is significant only in thalamic area.ConclusionThe metabolism of amino acids, as indicated by activities of specific transaminases, of brain is altered in response to aluminum exposure. These alterations are region specific and are dependent on dietary protein intake or manipulation of the brain amino acid homeostasis.

Effect of cadmium, mercury and copper on partially purified hepatic flavokinase of rat.

The effect of cadmium (Cd2+), mercury (Hg2+) and copper (Cu2+) was studied with partially purified flavokinase (ATP:riboflavin 5′-phosphotransferase EC 2.7.1.26) from rat liver. All the divalent heavy metal cations inhibited flavokinase activity in a concentration-dependent manner. The inhibitory effect of cadmium on the enzyme was completely reversed by increasing concentration, of Zinc (Zn2+) indicating a competition between Zn2+ and Cd2+ for binding with the enzyme. A competition between riboflavin and Cd2+ is also evident from the present investigation. These observations hint at the possibility that Zn2+ and Cd2+ probably compete for the same site on the enzyme where riboflavin binds. However, inhibition of flavokinase by Hg2+ could not be reversed by Zn2+. Our studies further reveal that hepatic flavokinase appears to contain an essential, accessible and functional thiol group(s) which is evident from a concentration dependent inhibition of activity by sulfhydryl reagent s like parachloromercuribenzoate (PCMB), 5,5′-dithiobis (2-nitrobenzoic acid)(DTNB), and N-ethylmaleimide (NEM). Inhibition of flavokinase by sulfhydryl reagents were protected, except in case of NEM inhibition, when the enzyme was incubated with thiol protectors like glutathione (GSH) and dithiothreitol (DTT). Furthermore, the enzyme could also be protected from the inhibitory effect of Cd2+ and Hg2+ by GSH and DTT suggesting that Cd2+ probably interacts with a reactive thiol group at or near the active site of enzyme in bringing about its inhibitory effect. (Mol Cell Biochem 167: 73-80, 1997)

Effect of cadmium treatment on hepatic flavin metabolism

Abstract The effect of cadmium on levels of hepatic riboflavin, flavin mononucleotide (FMN), flavin adenine dinucleotide (FAD), as well as the activities of flavokinase and FMN-phosphatase were studied following injection of cadmium sulfate solution subcutaneously to male. Sprague-Dawley rats at a dose of 0.44 mg/kg body weight, every alternate day for 15 days. The body weights and wet weights of liver were found to increase significantly following cadmium treatment ( P P P P P > 0.05, respectively). A significant decrease in activities of hepatic flavokinase and FMN-phosphatase were observed both in in vivo and in vitro experiments, although the degree of inhibition was found to be more pronounced in case of flavokinase than FMN-phosphase ( P P

On the metabolism of ascorbic acid in emetine-treated rats

Emetine reduces the rate of urinary ascorbic acid elimination in rats, the livers of which contained less L-ascorbic acid (Diamant, Halevy & Guggenheim, 1955) as a result of a reduction in L-ascorbic acid synthesis (Chatterjee, Datta & Ghosh, 1972). We have examined the effect of emetine on the oxidation by liver homogenates of L-gulonolactone to L-ascorbic acid, and the conversion of D-glucuronolactone to its free acid and of dehydro-L-ascorbic acid to 2,3-diketogulonic acid. Male Wistar rats, 90-110 g, were divided into two groups of equal average body weight. One group was injected subcutaneously with emetine hydrochloride (0.2 mg day-l for each 100 g wt) for 10 days. The other group served as pair-fed controls. The animals were maintained on a 18 % casein diet, details of which were reported by Chatterjee & others (1972). The rats were killed under light ether anaesthesia 24 h after the tenth dose. Blood was collected from the hepatic vein and serum was separated by centrifugation. The livers were chilled in ice. The L-gulonooxidase activity was assayed in a test system containing sodium phosphate buffer, pH 7.4 (20 mM), L-gulonolactone (5 mM), sodium pyrophosphate (50 mM), KCN (1 mM) and liver homogenate (in 0.25111 sucrose) equivalent to 100 mg fresh tissue (for details see Chatterjee & others, 1972). The uronolactonase activity of liver homogenate (in 0 . 1 5 ~ KCl) was determined by the method of Eisenberg & Field (1956), the dehydroascorbatase activity of liver tissues (homogenized in 0.1 5~ KCl) was according to Kagawa, Takiguchi & Shimazono (1961) as described by Mukherjee, Kar & others (1968) and the protein content of liver homogenate according to Gornall, Bardawill & David (1949). Urine samples were collected for 24 h after the 2nd, 5th and last injections of emetine and their ascorbic acid contents were determined by the method of Roe & Kuether (1943). The results show that emetine treatment for 10 days diminished both the in vitro L-ascorbic acid synthesizing ability and the dehydroascorbatase activity of the liver tissues of rats and these reductions were significant when the results were expressed on both a protein weight and a tissue weight basis (Table 1). Emetine treatment did

Effect of chromium on certain aspects of metabolic toxicities.

The impact of chromium exposure was studied in the liver, kidney, testis, spleen, cerebrum, and cerebellum of male Wistar rats (80-100 g body weight). It was observed that treatment of rats with chromium (ip, at a dose of 0.8 mg/100 g body weight/day) for a period of 28 days caused significant increase in chromium content while lowering the body weight along with the organ weight, except for the liver. It was also observed that there was a significant decrease in the DNA content of various organs tested. Also, a significant decrease in RNA content was observed in all the organs tested except for the testes. The liver, cerebrum, and cerebellum showed significant decreases in total protein content in chromium-treated animals, whereas the kidney, testes, and spleen showed insignificant alterations. The RNase activity was found to be significantly increased only in the testes and cerebrum. Pronase activity was significantly increased in the tissues, except for the liver. The glutamic-pyruvic acid transaminase activity decreased in all the tissues studied. On the other hand, glutamic-oxaloacetic acid transaminase activity increased in the liver, cerebrum, and cerebellum while decreasing in the kidney and spleen. It is suggested that chromium exposure at the present dose and duration induces metabolic toxicity in the form of depressive effects on nucleic acids and altered activities of RNase, pronase, and transaminases in tissues. The extent of such alterations varies from tissue to tissue and is in some cases diverse in nature.