Effect of azo-dye carcinogenesis on enzymes concerned with urea synthesis in rat liver

The evaluation of early stage oxidative status in streptozotocin induced diabetes in rats

Early-stage diabetes can be defined as the stages before absolute insulin deficiency in patients. In this study, the early stage oxidative effect of streptozotocin(STZ) induced diabetes mellitus was evaluated. 28 male adult Sprague-Dawley rats were divided into four groups; control group and 7th, 14th, 21st days diabetic groups. Diabetic groups received single 65 mg/kg STZ injection intraperitoneally. Rats were decapitated at 7th, 14th and 21st days, liver tissues were taken. Nitric oxide(NO), malondialdehyde(MDA) levels and catalase, arginase activities were measured. MDA and NO levels were increased (respectively p < .001 and p < .01), mainly 14 and 21 days after STZ administration; moreover, while liver catalase activity was progressively decreased (p < .001), oppositely arginase was increased in the same time period (p < .01). Results show that MDA and nitric oxide together with catalase and arginase switch at an early stage of diabetes and they may contribute to subsequent complications related to diabetes via increased oxidative damage.

Synthesis, Characterization, Molecular Modeling, and DNA Interaction Studies of Copper Complex Containing Food Additive Carmoisine Dye

A copper complex of carmoisine dye; [Cu(carmoisine)2(H2O)2]; was synthesized and characterized by using physico-chemical and spectroscopic methods. The binding of this complex with calf thymus (ct) DNA was investigated by circular dichroism, absorption studies, emission spectroscopy, and viscosity measurements. UV-vis results confirmed that the Cu complex interacted with DNA to form a ground-state complex and the observed binding constant (2× 10(4) M(-1)) is more in keeping with the groove bindings with DNA. Furthermore, the viscosity measurement result showed that the addition of complex causes no significant change on DNA viscosity and it indicated that the intercalation mode is ruled out. The thermodynamic parameters are calculated by van't Hoff equation, which demonstrated that hydrogen bonds and van der Waals interactions played major roles in the reaction. The results of circular dichroism (CD) suggested that the complex can change the conformation of DNA from B-like form toward A-like conformation. The cytotoxicity studies of the carmoisine dye and its copper complex indicated that both of them had anticancer effects on HT-29 (colon cancer) cell line and they may be new candidates for treatment of the colon cancer.

Effects of folic acid and methotrexate on arginase activity in regenerating rat liver tissue

Arginase (L-arginine-ureidohydrolase, EC 3.5.3.1) catalyses the hydrolysis of arginine to ornithine and urea. Its primary metabolic role is to remove the excess of ammonia through synthesis of urea. Ornithine, as a product of arginase reaction can be used for synthesis of polyamines. Rapid tissue growth after partial hepatectomy is accompanied by an increase in biosynthesis of polyamines. The aim of this study was to examine the importance of arginase in regenerating liver after partial hepatectomy and to investigate the influence of folic acid and methotrexate on arginase activity on this model of compensatory growth. It was established that arginase activity was significantly reduced in regenerating rat liver tissue at different time intervals after partial hepatectomy. Administration of folic acid to hepatectomized rats led to inhibition of arginase activity. Administration of methotrexate after hepatectomy increased the arginase activity.

Changes in enzyme activities in the urine and tissues of rats fed sodium o-phenylphenate

The activities of certain enzymes in the urine and tissues of rats given 2% sodium o- phenylphenate in the diet for 20 wk were examined. Urinary gamma-glutamyl transpeptidase (gamma GTP) decreased immediately after the start of feeding of the treated diet and its activity remained low for 20 wk. The gamma GTP and alkaline phosphatase (ALP) activities in kidney homogenate decreased to about 80% of the control at 20 wk, but G6PD activity was significantly increased; Na,K-ATPase was unchanged. On the other hand, the gamma GTP activity in the liver homogenate of treated rats was increased to about eight times that of the controls, the G6PD activity showed a significant increase, but the ALP and Na, K-ATPase activities were not significantly different from the control values. The glutathione concentration in the livers of treated rats was significantly reduced.

Arginase activity of different cells in tissue culture

Arginase activity was measured in ten different cell lines and all of them showed arginase activity. However, the amount of the activity in the cells varied more than 1000-fold. The cell density did not appear to affect the arginase activity much, since cultures of human fibroblasts grown to different cell densities exhibited only small variations in arginase activity. Arginase activity was in general higher than that of ornithine decarboxylase and there was no correlation between the two activities. When human fibroblasts were stimulated to proliferate in serum-free medium by adding certain growth factors the activity of ornithine decarboxylase increased markedly prior to the DNA synthesis, while the arginase activity increased more slowly and to a much smaller degree. Two cell lines, baby hamster kidney and mouse 3T3 cells, had low arginase activity when adapted to grow in serum-free medium, but in spite of this they were able to grow in serum-free medium without exogenous ornithine.

The differential contribution of arginase and transamidinase to ornithine biosynthesis in two achromic human melanoma cell lines

Cellular ornithine biosynthesis could be expected to play a significant role in putrescine formation and hence in growth. Two enzymes are involved in ornithine biosynthesis: arginase and transamidinase. These enzyme activities were studied in two human melanoma cell lines differing in their Km of diamine oxidase for putrescine and in their tumorigenicity in nude mice. Arginase activity accounts for the majority of ornithine formed in the highly tumorigenic cell line, while the majority of ornithine is derived from transamidinase action in the poorly tumorigenic cell line, with concomitant formation of methyl guanidine, a potent inhibitor of diamine oxidase.

Characterization of arginase activity from mouse epidermis and its relation to ornithine decarboxylase induction by the tumor-promoting agent, 12-O-tetradecanoylphorbol-13-acetate

Arginase, which catalyzes the cleavage of L-arginine to urea and ornithine, was detected in both soluble and particulate fractions of mouse epidermis. In a typical experiment, about 75 and 25% of the total arginase activity was associated with the soluble (100 000 X g supernatant) and the washed particulate fraction, respectively. Both soluble and particulate enzymes required the presence of divalent Mn2+ for activity. Arginase activity was increased by about 50% in the particulate fraction, but not in the soluble fraction, by preheating the fractions at either 50 or 55 degrees C in the presence of 15 mM MnCl2. Enzyme activity in both fractions, in the absence of 15 mM MnCl2, dropped precipitously during heating. A comparison of the nature of arginases in the soluble and particulate fractions revealed similar Km values (13 mM) and pH optima (9.5) and identical heat denaturation curves. Application of 10 nmol of 12-O-tetradecanoylphorbol-13-acetate to mouse skin did not increase arginase activity in either fraction over a period of 24 h. In contrast, there was a large increase in ornithine decarboxylase activity in the soluble fraction 4.5 h after treatment. Mouse epidermal ornithine decarboxylase activity was much less than arginase activity and was predominantly localized in the soluble fraction. These results indicate that the normal level of arginase activity is not a limiting factor for the stimulation of polyamine biosynthesis by TPA. High arginase activity in mouse epidermis may play a role in providing ornithine for polyamine biosynthesis and in the production of glutamate and proline as well as in the production of keratinous proteins.

A new look at the measurement and interpretation of enzyme assays

Some methodological problems in clinical enzymology, including instability of enzymes in the incubation mixture and requirements for optimal reaction conditions, are highlighted. The importance of a knowledge of fundamental enzyme biochemistry and physiology as the basis for their diagnostic application is stressed, and the different behaviour of some hepatic enzymes--namely, GOT, GPT, gamma-GT, and OCT, in various pathological conditions is traced back to their characteristic biochemical and physiological properties. In the field of urinary enzymes a knowledge of the ideal requirements for the enzyme investigation of the various renal functions and of the properties of potentially valuable enzymes permits a critical selection of the really useful ones.

Studies on progressive metabolic alterations in thioacetamide induced hepatocarcinogenesis

Sequential studies on levels of glycogen and lactic acid as well as activities of glucose-6-phosphatase, fructose-1, 6-diphosphatase aldolase, aspartic and ornithine transcarbamylase, arginase and xanthine oxidase were carried out in liver and tumour tissue of mice fed with 0.03% thioacetamide in normal stock diet. It was observed that significant decrease in glycogen content and activities of gluconeogenic enzymes was apparent at the age of 4 months, i.e. 2 months after thioacetamide treatment. Alterations in the other parameters studied were observed later, i.e. at the age of 9 months. Maximum changes were observed in the hepatomas, i.e. at the age of 17 months.

Variation of the enzymes of the urea cycle and aspartate transcarbamylase in liver of pregnant rats

The variations in the specific activities of the enzymes of the urea cycle were studied in the livers of pregnant rats and also in the livers of male rats and other females with the same body weight. The specific activities of the five enzymes of the urea cycle are the same in male and in female except for argininosuccinase. The activity of this enzyme is twice as high in female rats as in male rats. In pregnancy, the activities of the enzymes of the urea cycle are decreased except for arginase, which increases. Aspartate transcarbamylase remains constant during the same period.These results lead to the supposition that another pathway for the synthesis of orotic acid may exist, or more probably that there exist two carbamyl phosphate synthetases, one for pyrimidine biosynthesis and one for urea synthesis.

Effect of ethionine treatment on the activity of enzymes concerned with urea synthesis in rat liver

1. The activities of the enzymes of the urea cycle were measured in rat liver after feeding with a diet containing ethionine for 2 weeks. This treatment resulted in a decrease in the activity of ornithine transcarbamoylase, which fell to half the control value, while arginase increased by about 40%. The remaining enzymes of the urea cycle were unchanged at this time of treatment. These results are discussed in relation to the known effects of ethionine on nucleic acid synthesis. 2. The activities of glucose 6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase were measured in rat liver after feeding with a diet containing ethionine for 2 or 5 weeks. At the shorter time-period glucose 6-phosphate-dehydrogenase activity was more than doubled but 6-phosphogluconate-dehydrogenase activity remained unchanged. 3. The results are compared with similar measurements made after feeding with diets containing 4-dimethylamino-3'-methylazobenzene for 2 weeks. Striking similarities were found in the pattern of change in the enzyme activities of each of the pathways in the two treatments.

Activities of some enzymes concerned with citrate and glucose metabolism in transplanted rat hepatomas

1. Certain enzymes concerned with citrate and glucose metabolism have been measured in two transplanted rat hepatomas, one induced with ethionine (minimal deviation type) and one induced with dimethylaminoazobenzene. In these hepatomas both citrate-cleavage enzyme and NADP-linked isocitrate dehydrogenase in the soluble fraction of the cell were approximately one-third of the values for normal rat liver. These changes have been discussed in relation to the increased citric acid content of tumours and depressed rate of fatty acid synthesis. 2. The glucose-ATP-phosphotransferase activity was below normal liver values in the ethionine-induced tumour but greater than normal in the dimethylaminoazobenzene-induced hepatoma. The apparent K(m) values for the glucose-ATP phosphotransferases of these hepatomas were approx. 8x10(-5)m; no evidence was found for an enzyme with a high K(m) for glucose equivalent to liver glucokinase. 3. Of the enzymes of the pentose phosphate pathway, glucose 6-phosphate-dehydrogenase activity was three to five times as great whereas 6-phosphogluconate-dehydrogenase activity was the same or lower than normal liver in the ethionine-and dimethylaminoazobenzene-induced tumours respectively.