RESUMEN
Molecular mechanisms of chromatin damage have been investigated during tetrachloromethane and chlorophos intoxication of experimental animals. Introduction of tetrachloromethane to experimental animals induced chromatin degradation causing a partial loss of histone H1-DNA fragmentation and formation of intermolecular bonds: DNA-protein. Intoxication with chlorophos results in repression of a part of genes due to augmented chromatin compactness. Preventive introduction of the steroid preparation from Serratula coronata L. to experimental animals exerts a genoprotective effect, probably, as a result of derepression of genes responsible for reparation of chromatin structure.
Asunto(s)
Intoxicación por Tetracloruro de Carbono/tratamiento farmacológico , Cromatina/efectos de los fármacos , Daño del ADN , Hígado/efectos de los fármacos , Esteroides/farmacología , Triclorfón/envenenamiento , Animales , Intoxicación por Tetracloruro de Carbono/genética , Ecdisteroides , Masculino , Plantas Medicinales , Ratas , Ratas WistarRESUMEN
Marked changes in the structural and functional characteristics of liver nuclear chromatin fractions are observed under experimental D-hypovitaminosis, which differ in the degree of transcriptional activity. DNA-polymerase activity and activity of the fraction, enriched with RNA-polymerase I, increases in the active fraction. Free radical LPO reactions are modified in the chromatin fraction with low activity and to the less degree in the active one. Disturbances of chromatine structural properties are caused with the change in the protein and lipid components of chromatin. Administration of ecdysterone preparations (separately and together with vitamin D3) has a partial corrective effect on structural and functional organization of nuclear chromatine. At the action of ecdysterone normalization of LPO reactions modified by pathological changes is observed in the chromatin fraction with low activity and to the less degree in the active one. This kind of influence corrects to the less degree chromatin functional activity and quantitative and qualitative modifications of its protein component. Simultaneous influence of ecdysterone and vitamin D3 leads to the partial normalization of the biochemical indices studied (except for those which characterize LPO reactions) mainly in the active chromatin fraction.
Asunto(s)
Colecalciferol/farmacología , Cromatina/química , Ecdisterona/farmacología , Hígado/química , Deficiencia de Vitamina D/metabolismo , Animales , Fraccionamiento Químico , ADN Polimerasa Dirigida por ADN/efectos de los fármacos , ADN Polimerasa Dirigida por ADN/metabolismo , ARN Polimerasas Dirigidas por ADN/efectos de los fármacos , ARN Polimerasas Dirigidas por ADN/metabolismo , Peroxidación de Lípido/efectos de los fármacos , Hígado/efectos de los fármacos , Masculino , Ratas , Ratas Wistar , Relación Estructura-Actividad , Transcripción GenéticaRESUMEN
E-hypovitaminosis-induced antioxidant deficiency in rats causes changes in some properties of nuclear structures of the liver cells, i.e. fractions of transcriptionally active and repressed chromatin and nuclear matrix. Changes are found in the protein spectrum of the fraction of transcriptionally active chromatin and nuclear matrix. Lipids of transcriptionally active and repressed chromatin fractions may be peroxidated when this process is stimulated in the NADPH- and ascorbate-dependent systems. In antioxidant deficiency these processes are intensified in the fractions of repressed chromatin. E-hypovitaminosis leads to changes in the fatty acid spectrum of chromatin fractions which correlated with the shifts in the process of lipid peroxidation. Antioxidant deficiency produces changes in the activities of endogenous DNA- and RNA-polymerases in chromatin fractions and in the nuclear matrix. In the fraction of the transcriptionally active liver chromatin of E-deficient animals the endogenous total DNA-polymerase activity and the activity of DNA-polymerases alpha and beta decrease, while in the fractions of repressed chromatin the total RNA-polymerase activity increases. In E-hypovitaminosis the endogenous DNA- and RNA-polymerase activities in the nuclear matrix decrease. Addition of alpha-tocopherol to the preparations of the isolated nuclear matrix results in an increase of the DNA- and RNA-polymerase activities which is more vivid in preparations made of the E-hypovitaminous animal liver.
Asunto(s)
Núcleo Celular/metabolismo , Hígado/metabolismo , Deficiencia de Vitamina E/metabolismo , Animales , Cromatina/metabolismo , ADN Polimerasa Dirigida por ADN/metabolismo , ARN Polimerasas Dirigidas por ADN/metabolismo , Femenino , Metabolismo de los Lípidos , Matriz Nuclear/metabolismo , Proteínas Nucleares/metabolismo , RatasRESUMEN
The fractions of transcriptionally active and repressed chromatin of the rat liver include lipids, whose fatty acid residues are the substrates of lipid peroxidation (LP) processes. In vitro incubation in NADPH- and ascorbate-dependent LP systems resulted in the activation of peroxidation in the liver chromatin of intact animals, estimated from malonic dialdehyde (MDA) accumulation, the LP processes proceeding more intensely in the fractions of transcriptionally active vs. repressed chromatin. This correlates with the content of LP substrates in these fractions. Single administration of tetrachloromethane stimulated LP (estimated from the content of diene conjugates) in the fraction of transcriptionally active chromatin. The intensity of MDA accumulation increased in the repressed chromatin fraction of animals with stimulated LP vs. the control. In animals with stimulated LP the changes in the thermodenaturation parameters of chromatin fractions were observed, being more expressed in the transcriptionally active fraction. In view of the temporal coincidence of the LP intensification in chromatin and of its structural-functional reconstruction, the alteration of intensity of LP processes in chromatin may be considered as a factor of regulation of functional activity of the genome.
Asunto(s)
Cromatina/metabolismo , Peroxidación de Lípido , Hígado/metabolismo , Animales , ARN Polimerasas Dirigidas por ADN/metabolismo , Ácidos Grasos/metabolismo , Femenino , Calor , Malondialdehído/metabolismo , Desnaturalización de Ácido Nucleico , Desnaturalización Proteica , Ratas , Ratas EndogámicasRESUMEN
The transcriptional activity, nucleosomal patterns, and thermodenaturation parameters of low-active and active fractions of liver chromatin were studied in adult (6-8 mo) and old (26-28 mo) rats at 2, 4, and 6 weeks after partial hepatectomy. At 2 weeks postoperatively, there was a decrease in relative specific radioactivity (RSR) of the active chromatin fraction in adult rats, which returned to normal by the 4th week, while in the low-active fraction it was decreased throughout all the studied regeneration periods. The decrease of the low-active fraction RSR was attended with changes in the nucleosomal organization and DNA-protein interactions revealed by electrophoresis and thermodenaturation. Old rats were found to have the active fraction RSR unchanged throughout all the studied regeneration periods. The low-active fraction RSR increased at 2 and 4 postoperative weeks and decreased to the level of intact liver at 6 weeks. Electrophoretic analysis and parameters of thermodenaturation of the low-active fraction reflect changes in the chromatin conformation associated with transcription activation and, at the same time, reveal its higher compactness in nucleosomal structures. Age differences in the time-course of structural rearrangements and transcriptional activity of liver chromatin during regeneration may be responsible for different rates of postoperative liver restoration in adult and old rats.