RESUMO
BACKGROUND: Combined inheritance of genetic variants in ferrochelatase gene (FECH) are implicated in clinical manifestation of Erythropoietic Protoporphyria (EPP). OBJECTIVE: Identify the genetic variants in FECH gene and their associations in the expression of EPP in Argentina. Determine the allelic frequency of polymorphic variants, associations in cis and its linkage disequilibrium. METHODS: The FECH gene was PCR-amplified and sequenced. Allelic variants of intragenic polymorphisms were identified by PCR followed by sequencing or restriction digestion analysis. Residual FECH activity was determined by prokaryotic expression in Escherichia coli JM109. Data were analyzed using Haploview and Statistix 9. RESULTS: Ten mutations were identified: three novel (p.S222N; p.R298X and p.R367X) and seven already known (g.12490_18067del; p.R115X; p.I186T; c.580_584delTACAG; c.598 + 1 G>T; p.Y209X and p.W310X). The p.R115X mutation was found in two families. The p.S222N mutation expressed 5% of normal activity. Only individuals who inherited a mutation combined in trans to a low expression allele c.1-251G, c.68-23T, and c.315-48C, showed clinical symptoms. The absence of c.315-48C variant was sufficient for not triggering EPP. However, these variants showed high levels of cosegregation and GTC haplotype is over-represented in EPP patients. CONCLUSION: In the dominant inheritance form of EPP, c.315-48C variant in trans to the mutated allele is sufficient to trigger the disease. The presence of GTC haplotype in all patients with dominant EPP could be due to the high level of cosegregation of c.315-48C with c.1-251G and c.68-23T variants in our population.
Assuntos
Ferroquelatase/genética , Variação Genética , Protoporfiria Eritropoética/genética , Adolescente , Adulto , Argentina , Criança , Pré-Escolar , Humanos , Pessoa de Meia-Idade , Mutação , Polimorfismo Genético , Protoporfiria Eritropoética/diagnóstico , Adulto JovemRESUMO
Erythropoietic Protoporphyria (EPP) is an inherited deficiency of ferrochelatase, the last enzyme of the heme pathway. Under general anaesthesia, some patients develop neurological dysfunction suggesting upregulation in heme biosynthesis similar to that described for acute porphyrias after xenobiotic administration. Our aim has been to evaluate whether Isoflurane induces alterations in the heme pathway in a mouse model for EPP. Administration of Isoflurane (a single dose of 2 ml/kg, i.p) to wild-type (+/+), heterozygous (+/Fechm1Pas) and homozygous (Fechm1Pas/Fechm1Pas) mice, was evaluated by measuring the activity of delta-aminolevulinic acid synthetase (ALA-S) and Porphobilinogen-deaminase (PBG-D) in different tissues, as well as Heme oxygenase (HO), cytochrome P-450, CYP2E1 and glutathione levels in liver. Porphyrin precursors were measured in 24 h-urine samples. Fechm1Pas/Fechm1Pas mice receiving anaesthesia show enhanced ALA-S and CYP2E1 activities in the liver and increased urinary excretion of porphyrin precursors. No alterations were found in either PBG-D or HO activities. Diminished glutathione levels suggest that anaesthesia may produce oxidative stress in these animals. In conclusion, Isoflurane induces ALA-S activity and increased excretion of porphyrin precursors in EPP mice. These findings appear to confirm our previous hypothesis and indicate that Isoflurane may be an unsafe anaesthetic not only for patients with acute porphyrias but also for individuals with non acute porphyrias.
Assuntos
5-Aminolevulinato Sintetase/metabolismo , Isoflurano/farmacologia , Fígado/efeitos dos fármacos , Fígado/enzimologia , Protoporfiria Eritropoética/metabolismo , Animais , Ativação Enzimática/efeitos dos fármacos , Indução Enzimática/efeitos dos fármacos , Glutationa/metabolismo , Heme Oxigenase (Desciclizante) , Hidroximetilbilano Sintase/metabolismo , Camundongos , Camundongos Mutantes , Estresse Oxidativo/efeitos dos fármacosRESUMO
Porphyrias are a family of inherited diseases, each associated with a partial defect in one of the enzymes of the heme biosynthetic pathway. In six of the eight porphyrias described, the main clinical manifestation is skin photosensitivity brought about by the action of light on porphyrins, which are deposited in the upper epidermal layer of the skin. Porphyrins absorb light energy intensively in the UV region, and to a lesser extent in the long visible bands, resulting in transitions to excited electronic states. The excited porphyrin may react directly with biological structures (type I reactions) or with molecular oxygen, generating excited singlet oxygen (type II reactions). Besides this well-known photodynamic action of porphyrins, a novel light-independent effect of porphyrins has been described. Irradiation of enzymes in the presence of porphyrins mainly induces type I reactions, although type II reactions could also occur, further increasing the direct non-photodynamic effect of porphyrins on proteins and macro-molecules. Conformational changes of protein structure are induced by porphyrins in the dark or under UV light, resulting in reduced enzyme activity and increased proteolytic susceptibility. The effect of porphyrins depends not only on their physico-chemical properties but also on the specific site on the protein on which they act. Porphyrin action alters the functionality of the enzymes of the heme biosynthetic pathway exacerbating the metabolic deficiencies in porphyrias. Light energy absorption by porphyrins results in the generation of oxygen reactive species, overcoming the protective cellular mechanisms and leading to molecular, cell and tissue damage, thus amplifying the porphyric picture.
Assuntos
Enzimas/metabolismo , Hemeproteínas/efeitos da radiação , Luz , Fármacos Fotossensibilizantes/metabolismo , Porfirias/metabolismo , Porfirinas/farmacologia , Porfirinas/efeitos da radiação , Escuridão , Heme , Humanos , Protoporfirinas/farmacologia , Espécies Reativas de Oxigênio , Dermatopatias/induzido quimicamente , Raios Ultravioleta/efeitos adversos , Uroporfirinas/farmacologiaRESUMO
Amiodarone (AD) is an effective antidysrythmic drug, however, there can be serious side effects, such as hepatic and neurological alterations, as well as skin photosensitization, as seen in porphyrias. Clinical signs in porphyrias might be triggered by the so-called porphyrinogenic drugs. Without sound basis, Amiodarone has been classified as an unsafe drug for porphyric patients. The aim of this work has been to study the effect of AD, both in vivo and in vitro, on heme metabolism. In the in vivo assays, the activities of 5-aminolevulinate synthetase (ALA-S), ALA dehydratase (ALA-D), porphobilinogenase (PBGase) and PBG-deaminase (PBG-D) in blood, liver, and kidney; hepatic and fecal porphyrins, urinary ALA, PBG and porphyrins in male mice strain CF1 treated with AD (100 mg i.p. daily) for 1 week and 1 month, were measured. No significanat differences were found for any of these parameters in the AD treated animals as compared to controls. In the in vitro experiments human blood, and mice blood, liver, and kidney, were used to measure the activities of ALA-S, ALA-D, PBGase, PBG-D and uroporphyrinogen decarboxylase, in the presence of varying concentrations of AD (0.0172-4.304 mM). AD did not modify any of the enzyme activities. All of the above biochemical parameters were studied in 17 cardiac patients under AD treatment for 3 to 20 years. Neither the activities of the heme enzymes, nor the levels of precursors and porphyrins in urine and plasma were altered. These findings clearly demonstrate that AD is a pharmacologically safe drug and can be used for the treatment of associated pathologies in porphyrias.
Assuntos
Amiodarona/uso terapêutico , Porfirias/tratamento farmacológico , Porfirinas/metabolismo , 5-Aminolevulinato Sintetase/sangue , 5-Aminolevulinato Sintetase/metabolismo , Amônia-Liases/sangue , Animais , Antiarrítmicos/uso terapêutico , Fezes/química , Cardiopatias/enzimologia , Cardiopatias/metabolismo , Humanos , Fígado/metabolismo , Masculino , Camundongos , Porfirias/enzimologia , Porfirias/metabolismo , Porfirinas/urinaRESUMO
Porphyrias are a family of inherited diseases, each associated with a partial defect in one of the enzymes of the heme biosynthetic pathway. In six of the eight porphyrias described, the main clinical manifestation is skin photosensitivity brought about by the action of light on porphyrins, which are deposited in the upper epidermal layer of the skin. Porphyrins absorb light energy intensively in the UV region, and to a lesser extent in the long visible bands, resulting in transitions to excited electronic states. The excited porphyrin may react directly with biological structures (type I reactions) or with molecular oxygen, generating excited singlet oxygen (type II reactions). Besides this well-known photodynamic action of porphyrins, a novel light-independent effect of porphyrins has been described. Irradiation of enzymes in the presence of porphyrins mainly induces type I reactions, although type II reactions could also occur, further increasing the direct non-photodynamic effect of porphyrins on proteins and macromolecules. Conformational changes of protein structure are induced by porphyrins in the dark or under UV light, resulting in reduced enzyme activity and increased proteolytic susceptibility. The effect of porphyrins depends not only on their physico-chemical properties but also on the specific site on the protein on which they act. Porphyrin action alters the functionality of the enzymes of the heme biosynthetic pathway exacerbating the metabolic deficiencies in porphyrias. Light energy absorption by porphyrins results in the generation of oxygen reactive species, overcoming the protective cellular mechanisms and leading to molecular, cell and tissue damage, thus amplifying the porphyric picture
Assuntos
Humanos , Enzimas/metabolismo , Hemeproteínas/efeitos da radiação , Luz , Fármacos Fotossensibilizantes/metabolismo , Porfirias/metabolismo , Porfirinas/farmacologia , Porfirinas/efeitos da radiação , Escuridão , Heme , Protoporfirinas/farmacologia , Espécies Reativas de Oxigênio , Dermatopatias/induzido quimicamente , Raios Ultravioleta/efeitos adversos , Uroporfirinas/farmacologiaRESUMO
BACKGROUND AND AIMS: Uroporphyrin and protoporphyrin produce alterations on 5-aminolevulinic acid dehydratase and porphobilinogen deaminase, as a result of a direct effect of porphyrins on the protein structure. With the aim of assessing the possible protection from the porphyrins effect on the proteins, some chemicals and the enzyme substrates were assayed. METHODS: Enzymes were pre-incubated with the protecting agents (beta-mercaptoethanol, dithiotreitol, hydroxylamine, succinic anhydride) or the corresponding substrates (delta-aminolevulinic acid and porphobilinogen), and then exposed to the porphyrins. All experiments were performed in the enzyme solutions after removing the porphyrins. RESULTS: The presence of sulfhydryl reagents partially protected both the enzyme activities and the content of total SH and free amino groups, but they did not prevent the appearance of molecular aggregates in the electrophoresis. Similar results were obtained in the presence of the corresponding substrates. Nucleophilic addition of hydroxylamine to the aromatic amino acids on the enzymes and blockage of their free amino groups did not prevent the direct effect of porphyrins, but these agents protected the enzyme activities from the photodynamic action of the tetrapyrroles, and also prevented the formation of molecular aggregates. However, an increased amount of free amino groups was observed, probably due to protein fragmentation. CONCLUSIONS: Porphyrins mainly affected the SH groups at or near the active site of the enzymes. Most of the free amino groups on the treated enzymes were involved in the formation of cross-links among the protein molecules. Protein fragmentation induced by porphyrins under UV light, and the consequent increased amount of free amino groups, were observed.
Assuntos
Heme/química , Hidroximetilbilano Sintase/química , Sintase do Porfobilinogênio/química , Protoporfirinas/química , Uroporfirinas/química , Animais , Bovinos , Heme/metabolismo , Hidroximetilbilano Sintase/metabolismo , Sintase do Porfobilinogênio/metabolismo , Conformação Proteica , Protoporfirinas/metabolismo , Especificidade por Substrato , Uroporfirinas/metabolismoRESUMO
La porfiria cutánea tarda (PTC) es un desorden del metabolismo del hemo caracterizado por una masiva pofirinuria e incremento de porfirinas plasmáticas, como consecuencia de una disminución en la actividad de la enzima uroporfirinógeno decarboxilasa. El signo clínico salente es una típica fotosensibilización cutánea. En este trabajo se realiza una revisión de la PCT como entidad clínica, considerando en particular la variante esclerodermiforme(PCTE). Se ha llevado a cabo un estudio bioquimico clínico completop de 16 pacientes argentinos y 3 españoles, entre un total de 102 y 35 PCT respectivamente. En el momento del diagnóstico, los valores de porfirinas urinarias oscilaron entre 400 y 10000 ug/24 h(VN=50-250 ug/24h), con un patron cromatográfico típico: 40-50 por ciento uroporfirinas; (VN= 100 por ciento coproporfirionas) e indice de porfirinas plasmáticas (IPP) entre 1,6 y 5,3 con =618nm (VN<1,3). La aparición de lesiones esclerodermiformes fue más frecuente en el grupo argentino (15,58 por ciento) que en el español (8,57 por ciento) y a su vez más común en hombres que en mujeres. Un 35,7 por ciento de las PCTE argentinas presentaron lesiones de calcinosis en las zonas típicas, pre y retro auriculares, cuero cabelludo cuello y triángulo de escote; en un solo caso calcificación en helix y antihelix del pabellon auricular. En un 80 por ciento se hallo alopecía porfírica cicatricial y en un 72 por ciento placas de esclerosis. En un 35 por ciento de las PCTE argentinas las lesiones esclerodérmicas mejoraron con el tratamiento. En un 25 por ciento de los casos, las lesiones fueron previas a la aparición de los signos clásicos de la PCT en otro 25 por ciento casi concomitantes y en el 50 por ciento a 1 año después. En conclusión, se ha observado una alta incidencia de la PCTE en la población de pacientes argentinos , mucho mayor que en la serie española y qu en las descriptas en la literatura, sin poderse establecer ninguna correlación con los nivelrs de porfirinas plasmáticas o urinarias, ni con el tiempo de evolución de la enfermedad y la aparición de las lesiones esclerodérmicas. Cabe notar que los resultados terapéuticos fueron más satisfactorios que los esperados(AU)
Assuntos
Humanos , Masculino , Feminino , Porfiria Cutânea Tardia/diagnóstico , Escleroderma Sistêmico/diagnóstico , Alopecia , Porfirinas/isolamento & purificaçãoRESUMO
La porfiria cutánea tarda (PTC) es un desorden del metabolismo del hemo caracterizado por una masiva pofirinuria e incremento de porfirinas plasmáticas, como consecuencia de una disminución en la actividad de la enzima uroporfirinógeno decarboxilasa. El signo clínico salente es una típica fotosensibilización cutánea. En este trabajo se realiza una revisión de la PCT como entidad clínica, considerando en particular la variante esclerodermiforme(PCTE). Se ha llevado a cabo un estudio bioquimico clínico completop de 16 pacientes argentinos y 3 españoles, entre un total de 102 y 35 PCT respectivamente. En el momento del diagnóstico, los valores de porfirinas urinarias oscilaron entre 400 y 10000 ug/24 h(VN=50-250 ug/24h), con un patron cromatográfico típico: 40-50 por ciento uroporfirinas; (VN= 100 por ciento coproporfirionas) e indice de porfirinas plasmáticas (IPP) entre 1,6 y 5,3 con =618nm (VN<1,3). La aparición de lesiones esclerodermiformes fue más frecuente en el grupo argentino (15,58 por ciento) que en el español (8,57 por ciento) y a su vez más común en hombres que en mujeres. Un 35,7 por ciento de las PCTE argentinas presentaron lesiones de calcinosis en las zonas típicas, pre y retro auriculares, cuero cabelludo cuello y triángulo de escote; en un solo caso calcificación en helix y antihelix del pabellon auricular. En un 80 por ciento se hallo alopecía porfírica cicatricial y en un 72 por ciento placas de esclerosis. En un 35 por ciento de las PCTE argentinas las lesiones esclerodérmicas mejoraron con el tratamiento. En un 25 por ciento de los casos, las lesiones fueron previas a la aparición de los signos clásicos de la PCT en otro 25 por ciento casi concomitantes y en el 50 por ciento a 1 año después. En conclusión, se ha observado una alta incidencia de la PCTE en la población de pacientes argentinos , mucho mayor que en la serie española y qu en las descriptas en la literatura, sin poderse establecer ninguna correlación con los nivelrs de porfirinas plasmáticas o urinarias, ni con el tiempo de evolución de la enfermedad y la aparición de las lesiones esclerodérmicas. Cabe notar que los resultados terapéuticos fueron más satisfactorios que los esperados
Assuntos
Humanos , Masculino , Feminino , Escleroderma Sistêmico/diagnóstico , Porfiria Cutânea Tardia/diagnóstico , Alopecia , Porfirinas/isolamento & purificaçãoRESUMO
Some alterations in the protein structure of delta-aminolevulinic acid dehydratase (ALA-D) and porphobilinogen deaminase (PBG-D) induced by uroporphyrin (URO) and prototoporphyrin (PROTO) have been observed previously. To obtain further evidence of these phenomena, the absorption and fluorescence spectra of ALA-D and PBG-D and the total protein content of sulfhydryl and free amino groups were analyzed after exposure of the enzymes to URO I and PROTO IX, ALA-D and PBG-D were partially purified from bovine liver and exposed to URO I or PROTO IX, both in the dark and under UV light. All experiments were performed in the enzyme solutions after removing the porphyrins. Absorbance spectra changes in the region of 220-300 nm were registered, indicating the interaction of the porphyrins with the molecular structure of the enzymes. The main changes in the fluorescence spectra were observed in the spectral region of 555 nm, and only slight modifications in the spectral region of 340-360 nm; moreover, alterations were stronger upon UV irradiation and in the presence of URO I when compared with darkness and PROTO IX. Variations in total SH groups would suggest the formation of disulfur bridges induced by URO I and the rupture of some S-S groups induced by PROTO IX. The effect of porphyrins on free amino groups would reflect a combination of cross-linking and fragmentation of proteins. Structural changes were observed when the enzymes were exposed to the porphyrin both in the dark or under UV light; however, they were stronger in the latter condition. These results suggest that porphyrins per se could act directly on the protein structure and that this action would be enhanced upon UV irradiation.
Assuntos
Heme/metabolismo , Hidroximetilbilano Sintase/química , Sintase do Porfobilinogênio/química , Porfirinas/farmacologia , Aminoácidos/análise , Aminoácidos/química , Animais , Bovinos , Fígado/enzimologia , Protoporfirinas/farmacologia , Espectrometria de Fluorescência , Espectrofotometria , Compostos de Sulfidrila/análise , Raios Ultravioleta , Uroporfirinas/farmacologiaRESUMO
En la porfiria cutánea tarda(PCT) hay una falla en la uroporfirinógeno decarboxilasa (Uro-D) hepática, como consecuencia se incrementa la concentración de porfirinas altamente carboxiladas. Enla PCT hereditaria la Uro-D está disminuída en sangre y es normal en la PCT adquirida. Parte de la población hemodializada presenta signos cutáneos que son histológica y morfológicamente semejantes a la PCT, asociado a niveles aumentados de porfirias plasmáticas. Se estudió el contenido de porfirinas plasmáticas y la actividad de la Uro-D eritrocitaria, en 12 pacientes hemodializados sin lesiones cutáneas, uno de ellos portador de PCT hereditaria. El contenido de porfirias en plasma estuvo aumentado(0,084 mas igual 0,,10 ug/ml; uroporfirina igual 80 por ciento, cproporfirina igual 20 por ciento) en 30 por ciento de los pacientes estudiados( valor normal: 0,048 mas igual 0,010 ug/ml; coproporfirina igual 100 por ciento). Las porfirinas plasmáticas del paciente PCT al inicio del tratamiento con S-adenosil-L-metionina fue: 1,71 ug/ml; uroporfirina igual 48 por ciento, firiaporfirina igual 41 por ciento hexaporfirina igual 7 por ciento, pentaporfirina igual 3 por ciento y coproporfirina igual 1 por ciento) y luego de 6 años, al final del tratamiento, los valores fueron: 0,089 ug/ml; uriporfirina igual 80 por ciento, firiaporfirina igual 20 por ciento. La remisión clínica se correlacionó con la bioquímica. En los pacientes hemodializados la actividad de URO_D estuvo dentro de los valores normales(12,45 mas igual 1,o U/ml GR), excepto en el portador de la PCT hereditaria en el cual la actividad estuvodisminuída al 50 por ciento. Estos resultados sugieren que la hemodialisis per se no modificaria a la actividad de URO-D eritrocitaria. (AU)
Assuntos
Humanos , Masculino , Feminino , Adulto , Diálise Renal/efeitos adversos , Porfiria Cutânea Tardia/sangue , Porfiria Cutânea Tardia/metabolismo , Porfirinas/sangueRESUMO
En la porfiria cutánea tarda(PCT) hay una falla en la uroporfirinógeno decarboxilasa (Uro-D) hepática, como consecuencia se incrementa la concentración de porfirinas altamente carboxiladas. Enla PCT hereditaria la Uro-D está disminuída en sangre y es normal en la PCT adquirida. Parte de la población hemodializada presenta signos cutáneos que son histológica y morfológicamente semejantes a la PCT, asociado a niveles aumentados de porfirias plasmáticas. Se estudió el contenido de porfirinas plasmáticas y la actividad de la Uro-D eritrocitaria, en 12 pacientes hemodializados sin lesiones cutáneas, uno de ellos portador de PCT hereditaria. El contenido de porfirias en plasma estuvo aumentado(0,084 mas igual 0,,10 ug/ml; uroporfirina igual 80 por ciento, cproporfirina igual 20 por ciento) en 30 por ciento de los pacientes estudiados( valor normal: 0,048 mas igual 0,010 ug/ml; coproporfirina igual 100 por ciento). Las porfirinas plasmáticas del paciente PCT al inicio del tratamiento con S-adenosil-L-metionina fue: 1,71 ug/ml; uroporfirina igual 48 por ciento, firiaporfirina igual 41 por ciento hexaporfirina igual 7 por ciento, pentaporfirina igual 3 por ciento y coproporfirina igual 1 por ciento) y luego de 6 años, al final del tratamiento, los valores fueron: 0,089 ug/ml; uriporfirina igual 80 por ciento, firiaporfirina igual 20 por ciento. La remisión clínica se correlacionó con la bioquímica. En los pacientes hemodializados la actividad de URO_D estuvo dentro de los valores normales(12,45 mas igual 1,o U/ml GR), excepto en el portador de la PCT hereditaria en el cual la actividad estuvodisminuída al 50 por ciento. Estos resultados sugieren que la hemodialisis per se no modificaria a la actividad de URO-D eritrocitaria.
Assuntos
Humanos , Masculino , Feminino , Adulto , Diálise Renal/efeitos adversos , Porfiria Cutânea Tardia/metabolismo , Porfiria Cutânea Tardia/sangue , Porfirinas/sangueRESUMO
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.
Assuntos
Hemeproteínas/efeitos da radiação , Liases/efeitos da radiação , Uroporfirinas/farmacologia , Amônia-Liases/efeitos da radiação , Elétrons , Sequestradores de Radicais Livres , Humanos , Peróxido de Hidrogênio/sangue , Radical Hidroxila , Hidroximetilbilano Sintase/efeitos da radiação , Oxigênio/sangue , Sintase do Porfobilinogênio/efeitos da radiação , Superóxidos/sangue , Uroporfirinogênio Descarboxilase/efeitos da radiaçãoRESUMO
The effect of uroporphyrin I (UI) on several cytosolic and mitochondrial enzymes (succinyl CoA synthetase, delta-aminolevulinic acid synthetase, rhodanese, lactate dehydrogenase) has been examined. All the enzymes were inactivated in the presence of the porphyrin both in the dark and under UV light.
Assuntos
L-Lactato Desidrogenase/antagonistas & inibidores , Tiossulfato Sulfurtransferase/antagonistas & inibidores , Uroporfirinas/farmacologia , 5-Aminolevulinato Sintetase/antagonistas & inibidores , Animais , Bovinos , Citoplasma/enzimologia , Inibidores Enzimáticos/farmacologia , Glutamato Desidrogenase/antagonistas & inibidores , Mitocôndrias Hepáticas/enzimologia , Mitocôndrias Musculares/enzimologia , Fármacos Fotossensibilizantes/farmacologia , Coelhos , Succinato-CoA Ligases/antagonistas & inibidores , Raios Ultravioleta/efeitos adversosRESUMO
1. The effect of the administration of several doses of Enflurane and Isoflurane (2 ml/kg, i.p., daily) on heme metabolism and glucose levels was studied. 2. Liver and kidney delta-Aminolevulinic acid synthetase (ALA-S) activities were 85% (P < 0.01) induced after the third dose of Enflurane, instead induction of this enzyme was only detected, in animals receiving one dose of Isoflurane. 3. Blood Porphobilinogenase and deaminase (50%, P < 0.01) inhibition was produced only when animals received a single dose of the anesthetics. 5. ALA-S induction observed after the third dose of anesthetics could be a consequence of long lasting depletion in heme synthesis produced by blocking at uroporphyrinogen level.
Assuntos
5-Aminolevulinato Sintetase/metabolismo , Amônia-Liases/metabolismo , Enflurano/farmacologia , Heme/metabolismo , Isoflurano/farmacologia , Animais , Relação Dose-Resposta a Droga , Glucose/metabolismo , Rim/enzimologia , Fígado/enzimologia , Camundongos , Camundongos EndogâmicosRESUMO
1. The action of uroporphyrin I on erythrocytic ALA-D activity under dark and light conditions was examined. 2. Photo and non-photoinactivation of ALA-D induced by uroporphyrin I were observed. 3. Both effects were dependent on uroporphyrin concentration, temperature and time of exposure of the protein to the porphyrin. 4. Light-dependent effect of uroporphyrin I is related with the phototoxicity of porphyrins and could be produced by primary amino acid photooxidation followed by secondary cross-linking of the protein. 5. Light-dependent effect of uroporphyrin I could be ascribed to a direct enzyme inhibition due to binding of the porphyrin to the protein inducing structural changes at or near its active site.
Assuntos
Escuridão , Luz , Sintase do Porfobilinogênio/antagonistas & inibidores , Uroporfirinas/farmacologia , Humanos , TemperaturaRESUMO
1. The effect of URO I on the activity of ALA-D, PBGase, deaminase and URO-D, both in aerobiosis and anaerobiosis, was studied. 2. Photoinactivation of the enzymes was much lower in an anaerobic than in an aerobic atmosphere. 3. Dark inactivation in the absence of oxygen was lower than its presence. 4. Preincubation in the presence of ALA or PBG protected the enzymic activity of ALA-D, PBGase and deaminase against URO I-inactivation both under u.v. light and in the dark. 5. Photoinactivating action of URO I would be mediated by reactive oxygen species generated by the excited porphyrin after its absorption of light. Dark inactivation, in aerobiosis, can also be partly mediated by amino acid oxidation, although to a lesser extent than that observed under u.v. light.
Assuntos
Escuridão , Inibidores Enzimáticos/farmacologia , Luz , Uroporfirinas/farmacologia , Aerobiose , Amônia-Liases/antagonistas & inibidores , Anaerobiose , Humanos , Hidroximetilbilano Sintase/antagonistas & inibidores , Sintase do Porfobilinogênio/antagonistas & inibidores , Uroporfirinogênio Descarboxilase/antagonistas & inibidoresRESUMO
The effects of isoflurane, a commonly used volatile anesthetic, on the activity of some haem enzymes in liver, kidney, and blood, and glucose content in liver and blood were studied. Mice were injected with different doses of the drug (0.5-6 mL/kg) and killed at varying intervals after injection (5-240 min). Within this dose range, optimal effects on alteration of haem metabolism were obtained at 2 mL/kg. The time-response profile for each enzyme was different. Blood porphobilinogenase (PBGase) and deaminase showed lower activities 20 min after anesthesia. This diminution coupled with the induction of delta-aminolevulinate synthetase activity observed soon after anesthesia (5 min) would fit well with the expected biochemical changes occurring in acute intermittent porphyria, indicating that this may be a suitable animal model for this disease.
Assuntos
Ativação Enzimática/efeitos dos fármacos , Isoflurano/farmacologia , Rim/efeitos dos fármacos , Fígado/efeitos dos fármacos , Porfiria Aguda Intermitente/induzido quimicamente , Animais , Modelos Animais de Doenças , Relação Dose-Resposta a Droga , Glucose/metabolismo , Isoflurano/administração & dosagem , Camundongos , Porfiria Aguda Intermitente/metabolismoRESUMO
1. The effect of enflurane, a volatile anesthetic, on heme metabolism was studied. Different doses (0.5-6.0 ml/kg) of this anesthetic were administered i.p. to mice and animals sacrificed at different times after administration (5-240 min). 2. The dose of 2 ml/kg was chosen as the optimum anesthetic dose producing more alterations in the heme pathway. 3. ALA-S was significantly induced at earlier times of anesthesia. 4. Blood PBGase and deaminase was greatly reduced. 5. This diminution coupled with ALA-S induction are in accordance with the known biochemical changes occurring in acute intermittent porphyria and include enflurane in the list of porphyrinogenic drugs, the use of which is not recommended for the management of anesthesia in porphyric patients.