C F Polo

University of Buenos Aires, Buenos Aires, Buenos Aires F.D., Argentina

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Publications (30)40.45 Total impact

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    ABSTRACT: Chemically induced and spontaneous liver tumors share some metabolic alterations. The decline in hemoprotein levels during hepatocarcinogenesis may result from a diminution of the intracellular heme pool. To elucidate if the onset of the pre-initiation stage alters the natural regulation mechanism of heme pathway, animals were fed with p-dimethylaminoazobenzene (DAB) and treated or not with 2-allylisopropylacetamide (AIA). The induction of 6-Aminolevulinic acid synthase (ALA-S) activity and the diminution in microsomal heme oxygenase (MHO) did not change when DAB fed animals were treated with AIA. Cytochrome P-450 (P-450) levels and glutathione S-transferase activity were increased in all the groups tested. Tryptophan pyrrolase, sulphatase and beta-glucuronidase activities were altered in DAB fed animals but AIA treatment did not produce any effect. Changes in drug metabolizing enzymes in livers of DAB fed animals could be the result of a primary deregulation of heme metabolism. These results give additional support to our hypothesis about a mechanism for the onset of hepatocarcinogenesis.
    Cancer biochemistry biophysics 08/1999; 17(1-2):25-34.
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    ABSTRACT: 1. The effect of in vitro glycation on delta-aminolevulinic dehydratase (ALA-D) under several experimental conditions was investigated. When preincubated with 500 mM glucose at 37 degrees C for 20 hr, ALA-D was 80% inactivated and glycated hemoglobin levels were increased more than fourfold. 2. Thiobarbituric acid species were not modified during glycation; therefore ALA-D inactivation cannot be attributed to glucose autoxidation. 3. Acetyl salicylic acid was effective in preventing both hemoglobin glycation and ALA-D inactivation by glucose. 4. A method has been developed for measuring protein glycation in vitro, in a crude preparation of red blood cells, which can also be applied to sugars other than glucose.
    General Pharmacology 10/1998; 31(3):441-5.
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    ABSTRACT: Oxidants play a role in several stages of carcinogenesis. A high antioxidant capacity is expected to protect 'initiated' cells from excessive oxidant toxicity. The aim of this study was to determine the chemopreventive effect of a-tocopherol (alpha-T) on the hepatocarcinogenesis induced with p-dimethylaminoazobenzene (DAB) in mice. The dietary administration of alpha-T completely reversed the induction of delta-aminolevulinate synthetase and glutathione-S-transferase (the tumoral marker enzyme). alpha-T greatly enhanced P 450 levels, which were even higher in animals exposed to DAB. Indirect evidence for the involvement of oxygen radicals in the DAB model of hepatocarcinogenesis was provided by increased levels of thiobarbituric acid reactive species, which were detected in animals with severe liver damage and were assessed by histological analysis. alpha-T reduced the degree of hepatic injury, although this vitamin produced only slight changes in the oxidative parameters evaluated. The use of alpha-T as a potential chemopreventive agent, particularly during the initiation stage of carcinogenesis provoked by DAB, is worthy of further study.
    European Journal of Cancer Prevention 02/1998; 7(1):69-76. · 2.97 Impact Factor
  • General Pharmacology 01/1998; 31(3).
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    ABSTRACT: 1.The effect of in vitro glycation on δ-aminolevulinic dehydratase (ALA-D) under several experimental conditions was investigated. When preincubated with 500 mM glucose at 37°C for 20 hr, ALA-D was 80% inactivated and glycated hemoglobin levels were increased more than fourfold.2.Thiobarbituric acid species were not modified during glycation; therefore ALA-D inactivation cannot be attributed to glucose autoxidation.3.Acetyl salicylic acid was effective in preventing both hemoglobin glycation and ALA-D inactivation by glucose.4.A method has been developed for measuring protein glycation in vitro, in a crude preparation of red blood cells, which can also be applied to sugars other than glucose.
    General Pharmacology-the Vascular System - GEN PHARMACOL-VASC SYST. 01/1998; 31(3):441-445.
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    ABSTRACT: 1.Male CF 1 mice were fed p-dimethylaminoazobenzene (DAB) for 35 days and received 5,5-diethylbarbituric acid, before or after DAB treatment, with the purpose of investigating whether the onset of the preinitiation stage of carcinogenesis alters the natural regulatory mechanism of the heme pathway.2.Changes detected in drug metabolizing enzymes are likely to be the consequence of a primary deregulation mechanism of heme metabolism, shown by an increase in δ-aminolevulinic acid synthetase activity and a decrease in microsomal heme oxygenase, which would finally lead to a great enhancement of cytochrome P450 levels.3.The alterations found here would give rise to a pattern distinctive to that usually observed in the so-called resistant hepatocyte.
    General Pharmacology 11/1997;
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    ABSTRACT: 1. The effect of long-term griseofulvin (GRIS) topical administration on some indicators of liver damage was examined. 2. Liver porphyrin accumulation was significant; however, no porhyrin crystals were observed under light microscopy. 3. An earlier onset of hepatopathy was established (3-fold) increase of direct bilirubin values after 7 days of treatment; hepatic injury was confirmed by measuring a 6-fold increase of free bilirubin. 4. Enhanced values of alkaline phosphatase and glutamic oxalacetic transaminase (GOT) confirmed the onset of cholestasis. 5. Topical application of GRIS induced measurable hepatopathy. Nevertheless, we cannot discard the possibility that this hepatopathy could also be attributed in part to a direct reaction to xenobiotics.
    General Pharmacology 09/1997; 29(2):207-10.
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    ABSTRACT: Rhodanese (thiosulphate:cyanide sulphurtransferase) shows distinctive mitochondrial and cytoplasmic activities in several models of tumorigenesis. To investigate the basis for these differences, the enzyme was purified from mitochondrial and cytosolic liver fractions of mice treated with the carcinogen p-dimethyl-aminoazobenzene (DAB) and some inhibition kinetic studies were carried out. When both substrates were assayed at inhibitory levels, non-competitive inhibition was observed for the second substrate at variable concentrations, the reversible connection between both substrates was attained by the instability of the second enzyme form. It is suggested that the enzyme might be changing from an unstable ES form to a more stable sulphur substituted intermediate as a consequence of DAB treatment. Sulphite was a competitive inhibitor vs thiosulphate for rhodanese isolated from normal liver and a hyperbolic activator for the enzyme isolated from liver of DAB-treated animals.
    Cancer biochemistry biophysics 07/1997; 15(4):285-93.
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    ABSTRACT: Aerobic and anaerobic studies have demonstrated that uroporphyrin I-induced inactivation of delta-aminolevulinic acid dehydratase, porphobilinogenase, deaminase and uroporphyrinogen decarboxylase was dependent on oxygen and mediated by reactive oxygen species. The mechanism of photoinactivation of those heme-enzymes from human erythrocytes by uroporphyrin I by u.v. light was investigated. Enzymes of the heme pathway were preincubated in the presence of specific scavengers for several reactive oxygen species and then exposed to uroporphyrin I and u.v. light. Upon exposure of the enzymes to the porphyrin under u.v. light, and in an aerobic atmosphere, the percentage of enzyme activities with respect to the corresponding controls were 50.2 +/- 5.1 (SD, n = 6), 25.3 +/- 3.0 (SD, n = 6), 25.9 +/- 2.8 (SD, n = 6) and 49.7 +/- 7.5 (SD, n = 8) for delta-aminolevulinic acid dehydratase, porphobilinogenase, deaminase and uroporphyrinogen decarboxylase, respectively. The presence of sodium azide, histidine or superoxide dismutase did not protect the enzymes against the effects of uroporphyrin I. However, both cysteine and potassium ferrycyanide prevented the enzyme photoinactivation induced by uroporphyrin I. In the presence of either catalase or GSH, the enzyme photoinactivation was lower. Ethanol, glucose and dimethylsulfoxide had no effect on enzyme activity, while ion chelators had variable effects. This study shows that the type II mechanism is not the predominant reaction mediating the uroporphyrin I effect and enzyme photoinactivation would involve an electron transfer. Hydrogen peroxide and hydroxyl radicals could possibly mediate the uroporphyrin I-induced enzyme photoinactivation.
    The International Journal of Biochemistry & Cell Biology 05/1996; 28(4):415-20. · 4.15 Impact Factor
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    ABSTRACT: The correlation between blood lead level (BLL), delta-aminolevulinate dehydratase (ALA-D) activity, and other common biochemical parameters used to assess a plumbism diagnosis have been carefully analyzed, with the aim of correctly interpreting the data handled in the laboratory. No correlation was observed between BLL and free erythrocyte porphyrins. In the case of ALA-D or Zn-reactivated ALA-D despite the direct correlation with BLL, the curve follows a potential or a logarithmic line, which is not the best to calculate BLL. The so-called Zn-ALA-D-reactivation index (iZn) has been defined as the ratio between the activity of Zn-reactivated ALA-D and the activity of ALA-D. The plot of BLL against the iZn revealed a very good linear relationship which allows an estimate of BLL with reasonable accuracy within a very wide range.
    Ecotoxicology and Environmental Safety 01/1996; 32(3):267-72. · 2.20 Impact Factor
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    ABSTRACT: Rhodanese (thiosulfate: cyanide sulfurtransferase) shows distinctive mitochondrial and cytoplasmic activities in several models of tumorigenesis. To investigate the basis for these differences, the enzyme was purified from the mitochondrial and cytosolic liver fractions of mice treated with the carcinogen p-dimethyl-aminoazobenzene (DAB) and some properties were studied. Mitochondrial and cytoplasmic rhodanese exhibited different responses to the effect of ionic strength, denaturants, sulphydryl reagents, lipids and detergents, but no significant difference between enzymes purified from controls or DAB treated animals was observed. It is important to note that although chemical studies did not show very striking differences between either of the rhodanese forms, fluorescence spectral studies suggested that in DAB-treated mice, the cytosolic rhodanese would be present almost completely as the sulfur-free form, while the mitochondrial enzyme would be present as the sulfur-substituted form. These findings would justify the high rhodanese activity present in mitochondria. On the other hand, in control animals, rhodanese would exist only as the partial sulfur-substituted form in both fractions.
    Cancer biochemistry biophysics 07/1995; 15(1):55-63.
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    ABSTRACT: Rhodanese (thiosulfate:cyanide sulfurtransferase, E.C. 2.8.1.1), an enzyme involved in heme regulation, showed distinctive mitochondrial and cytoplasmic activities in several models of tumorigenesis. To investigate the basis for these differences, the enzyme was partly purified and characterized from the mitochondrial and cytosolic liver fraction of mice treated with the carcinogen p-dimethyl-aminoazobenzene (DAB). A linear relationship between incubation time and specific activity was observed up to about 30 min for cytosolic enzyme and 15 min for mitochondrial enzyme irrespective of whether or not the enzyme was derived from treated or untreated animals. The optimum incubation temperature was 3 degrees C for the enzyme of both fractions in control animals and 30 degrees C for treated animals in both cases. In control and DAB treated animals the cytoplasmic rhodanese exhibited a maximum at a lower pH than for the mitochondrial enzyme. The enzyme showed typical Michaelis-Menten behavior with cyanide inhibition at concentrations higher than 25 mM for controls and 10 mM for treated animals for both fractions and thiosulfate inhibition at concentrations higher than 100 mM in all cases studied. Km values of 190 and 65.66 mM were obtained for thiosulfate and 6.37 and 9.79 mM for cyanide for both mitochondrial and cytosolic fractions of control animals; while Km values of 31.75 and 4.58 mM were obtained for thiosulfate and 0.61 and 1.11 mM for cyanide in both fractions of treated animals. We demonstrated differences in the kinetics for rhodanese derived from mitochondrial and cytoplasmic fractions of livers taken from tumor bearing mice. These differences might provide an explanation for the abnormalities of heme synthesis previously reported during hepatocarcinogenesis.
    The International Journal of Biochemistry & Cell Biology 06/1995; 27(5):523-9. · 4.15 Impact Factor
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    ABSTRACT: A frequent coexistence of diabetes and porphyria disease has been reported. Under normal conditions, porphyrin biosynthesis is well regulated to only form the amount of heme required for the synthesis of the various hemoproteins. The activity of some heme enzymes and rhodanese in streptozotocin (STZ) induced diabetic mice and in allylisopropylacetamide (AIA) induced experimental acute porphyria mice has been examined. The role of alpha-tocopherol (alpha-T), reported to prevent protein glycation in vitro, has also been investigated. AIA induced hepatic delta-aminolevulinic acid synthetase (ALA-S) activity in control animals but was ineffective in the diabetic group. alpha-Tocopherol did not modify ALA-S activity in either group. delta-Aminolevulinic acid dehydratase (ALA-D) and deaminase activities were significantly diminished both in liver and blood of diabetic animals. alpha-Tocopherol prevented inhibition of ALA-D, deaminase and blood rhodanese activities in diabetic animals but alpha-tocopherol by itself did not affect the basal levels of the enzymes studied. The potential use of alpha-tocopherol to prevent late complications of diabetes, including the onset of a porphyria like syndrome is considered.
    Chemico-Biological Interactions 05/1995; 95(3):327-34. · 2.97 Impact Factor
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    ABSTRACT: In the last decades several authors have observed a frequent association between diabetes mellitus and porphyria, mainly porphyria cutanea tarda. In previous studies, it has been demonstrated that both d delta d-aminolevulic acid dehydratase (ALA-D) and porphobilinogen deaminase (PBG-D), enzymes of the heme pathway, are inhibited by high concentrations of glucose in vitro in crude preparations of erythrocytes. The activity of these same enzymes was diminished in different tissues obtained from streptozotocin induced diabetic mice. Therefore, we decided to investigate the incidence of heme metabolism alterations in diabetes mellitus in a population of 100 non selected adult patients. The activities of erythrocytic ALA-D and PBG-D were measured. Rhodanese, an enzyme of the sulfocompounds pathway closely related to the regulation of heme biosynthesis, was also studied. Urine porphyrin content as well as the chromatographic pattern of esterified porphyrins were determined. ALA-D and PBG-D activities were diminished in diabetic patients (40% and 20% respectively), while rhodanese was only slightly increased (Fig. 1). ALA-D activity was subnormal in a 92% of the complete diabetic population, while PBG-D activity was less than normal in a 79% of the same population. No significative differences between enzymic activities were observed in the groups insulin and non-insulin dependent (Fig. 3). Urine porphyrin content was increased in 5% of the diabetic population. Chromatographic pattern of urinary porphyrins was notably altered in diabetic patients irrespectively of their porphyrin content (Fig. 4), suggesting an alteration in the enzyme uroporphyrinogen decarboxylase resembling the primary enzymic defect observed in porphyria cutanea tarda.(ABSTRACT TRUNCATED AT 250 WORDS)
    Medicina 02/1995; 55(2):117-24. · 0.42 Impact Factor
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    ABSTRACT: 1.1. Heme regulation before the appearance of hyperplastic nodules was investigated in mice models of hepatocarcinogenesis.2.2. With this aim 5-aminolaevulinate synthetase (ALA-S), microsomal heme-oxygenase (MHO), mitochondrial and cytoplasmic rhodanese activities were examined throughout a period of 35 days in animals exposed to dietary p-dimethylaminoazobenzene (DAB).3.3. ALA-S activity was significantly diminished (50%) on day 14, then showing a sharply rising profile from day 28 onwards, and reaching 350% on day 35.4.4. A similar profile was observed for mitochondrial rhodanese activity.5.5. Changes in MHO and cytoplasmic rhodanese activities were almost the opposite to those observed for ALA-S.6.6. The distinctive alteration in mitochondrial and cytoplasmic rhodanese would suggest that it plays a subtle role in ALA-S regulation during carcinogenesis initiation through a mechanism that appears to involved subcellular localization controls perhaps by means of the breakage of cystine trisulphide postulated to act as an ALA-S activator.7.7. Taking into account the present results, we suggest a probable mechanism for the onset of hepatocarcinogenesis that includes a primary activating liver status, provoking biochemical aberration leading to the stage of initiation of hepatocarcinogenesis involving the whole organ.
    Comparative biochemistry and physiology. B, Comparative biochemistry 10/1992; · 2.07 Impact Factor
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    ABSTRACT: 1. URO-D was investigated in crude extracts from mouse mammary carcinoma, normal mouse (NM) liver and tumor-bearing mouse (TBM) liver. 2. URO-D from TBM liver and tumor appears to be more sensitive to increasing concentrations of UROgen than the NM liver enzyme. 3. In tumor the rate-limiting step seems to be the decarboxylation of the first carboxyl group, but this was not so clear for the NM and the TBM liver URO-D. 4. URO-D activity was enhanced when incubated at higher temperatures in the presence of its substrate, suggesting that UROgen might afford some protection of the enzyme against heat inactivation. 5. The optimum pH for all three sources is around 7.0.
    Comparative biochemistry and physiology. B, Comparative biochemistry 06/1992; 102(1):87-92. · 2.07 Impact Factor
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    ABSTRACT: 1. Basal levels and allyl-isopropylacetamide (AIA) or veronal induced levels of delta-amino-levulinate synthetase (ALA-S), cytoplasmic and mitochondrial rhodanese were determined in tumor (T) and liver of both normal mice (NM) and T-bearing mice (TBM). 2. Rhodanese tumoral mitochondrial levels were higher than the hepatic normal mitochondrial fraction, while the cytoplasmic activity was nearly equal in all sources. 3. In neither case was the activity of tumoral ALA-S and rhodanese altered by any of the porphyrinogenic drugs. 4. Mitochondrial and cytoplasmic rhodanese activity was also measured in tumor and liver of TBM at different intervals after transplantation. We concluded that the behaviour of rhodanese is a property inherent to the tissue and not one attained with time.
    Comparative biochemistry and physiology. B, Comparative biochemistry 06/1992; 102(1):83-5. · 2.07 Impact Factor
  • C F Polo, E S Vazquez, A M Batlle
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    ABSTRACT: 1. delta-Aminolevulinic acid synthetase (ALA-S), rhodanese and microsomal heme oxygenase (MHO), were quantitated in Cl4C induced regenerating mouse liver. 2. Maximal hepatomegalia was observed at 48 hr after i.p. injection of a single dose of the toxin. 3. ALA-S activity decreased on day 2, and then significantly increased (50%) between days 3 and 7, returning afterwards to control values. 4. Cytoplasmic rhodanese, as well as MHO activities, exhibited a clear correlation as compared with the ALA-S activity profile. 5. Porphyrin biosynthesis from precursor delta-aminolevulinic acid (ALA) was significantly increased even after 15 days of intoxication. 6. Present results would indicate that Cl4C is acting in a dual fashion.
    Comparative biochemistry and physiology. B, Comparative biochemistry 01/1992; 101(1-2):243-6. · 2.07 Impact Factor
  • Comparative Biochemistry and Physiology Part B: Biochemistry and Molecular Biology - COMP BIOCHEM PHYSIOL B BIOCHEM MOL BIOL. 01/1992; 102(1):83-85.
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    ABSTRACT: 1. Porphobilinogenase (PBGase) and hydroxymethylbilane synthetase (HMB-S) were investigated in crude extracts from mouse mammary carcinoma, normal mouse liver and tumor bearing mouse liver. 2. A Michaelis-Menten kinetics for both enzymes in either source was observed. Km values of 87 to 108 microM, Vmax of 1.57-1.83 nmol porphyrins/2 hr and a Hill coefficient of n = 1 were obtained for PBGase and Km values of 13 to 19 microM and Vmax of 2.6-4.8 were obtained for HMB-S. 3. Porphyrin synthesis was linear up to 180 min of incubation in all cases for PBGase and HMB-S, and greatly increased with higher incubation temperature being maximal at 60 degrees C and nil at 70 degrees C, optimal temperature was 37 degrees C for either enzyme in either source. 4. Uroporphyrinogen III synthetase was heat inactivated while HMB-S was a heat stable enzyme. Optimum pH was 8.2 for PBGase and HMB-S in either tissue.
    Comparative biochemistry and physiology. B, Comparative biochemistry 02/1991; 98(1):67-71. · 2.07 Impact Factor