Rat Liver In Relation Research Articles

The effects of di(2‐ethylhexyl)phthalate on rat liver in relation to selenium status

This study was performed to determine the hepatotoxicity of di(2-ethylhexyl)phthalate (DEHP) in relation to selenium status. In 3-week-old Sprague-Dawley rats, selenium deficiency was induced by a ≤0.05 selenium mg/kg. A selenium supplementation group was given 1mg selenium/kg diet for 5weeks. Di(2-ethylhexyl)phthalate-treated groups received 1000mg/kg dose by gavage during the last 10days of the experiment. Histopathology, peroxisome proliferation, catalase (CAT) immunoreactivity and activity and apoptosis were assessed. Activities of antioxidant selenoenzymes [glutathione peroxidase 1 (GPx1), glutathione peroxidase 4 (GPx4), thioredoxin reductase (TrxR1)], superoxide dismutase (SOD), and glutathione S-transferase (GST); aminotransferase, total glutathione (tGSH), and lipid peroxidation (LP) levels were measured. Di(2-ethylhexyl)phthalate caused cellular disorganization while necrosis and inflammatory cell infiltration were observed in Se-deficient DEHP group (DEHP/SeD). Catalase activity and immunoreactivity were increased in all DEHP-treated groups. Glutathione peroxidase 1 and GPx4 activities decreased significantly in DEHP and DEHP/SeD groups, while GST activities decreased in all DEHP-exposed groups. Thioredoxin reductase activity increased in DEHP and DEHP/SeS, while total SOD activities increased in all DEHP-treated groups. Lipid peroxidation levels increased significantly in SeD (26%), DEHP (38%) and DEHP/SeD (71%) groups. Selenium supplementation partially ameliorated DEHP-induced hepatotoxicity; while in DEHP/SeD group, drastic changes in hepatic histopathology and oxidative stress parameters were observed.

Effects of Pregnancy, Age and Sex in the Metabolism of Styrene in Rat Liver in Relation to the Regulation of Cytochrome P450 Enzymes

To elucidate the effect of maternal styrene exposure, which is due to various postnatal changes in the development and behavior of offspring, we investigated pregnancy-induced changes in the metabolism of styrene in rat liver in relation to the regulation of cytochrome P450 enzymes. We also examined age and sex-induced changes in the metabolism of styrene. Pregnancy appeared to exert a negative effect on cytochrome P450 content at the late stage, whereas microsomal protein content showed little change during pregnancy. Pregnancy significantly decreased the rate of formation of styrene glycol at the late stage. The percentage of remaining activity in microsomes exposed to anti-CYP2E1 was lower than that exposed to anti-CYP2C11/6 in pregnant and non-pregnant female rats and immature male rats, indicating that CYP2E1 contributes to the metabolism of styrene more than CYP2C11/6 in these rats. Although pregnancy seemed to decrease styrene metabolism, the contribution of CYP2E1 seemed to be slightly increasing. In conclusion, pregnancy clearly influences the metabolism of styrene as well as other characteristic factors such as age and sex. It is very important to elucidate the changes in specific P450 isozyme composition related to their characteristic modification and in their affinity for chemicals.

The Circadian Rhythm in Activity of the Periodic Acid Schiff Reaction and of the Mg and Ca Content in Rat Liver in Relation to Age and Season of the Year

The experiments were carried out on male Wistar rats aged 6, 12 and 24 months, over the four seasons of the year. Analysis of the results obtained in all age groups disclosed that changes in activity of the p.a.S (periodic acid Schiff) reaction and in concentrations of Mg and Ca in the liver showed rhythmic oscillations with a period of 12 hours. The maximal p.a.S reaction activity and of Ca and Mg levels were generally found to coincide throughout all seasons and in all age groups. The rhythms of change in these parameters in 12- and 24-month-old rats showed a phase shift as compared to the 6-month-old animals.

Primary and Reversible Injury of H+-ATPase in Warm Ischemia and Reperfusion of Rat Liver in Relation to Intramitochondrial Adenine Nucleotide

The injury and recovery processes of complex reactions of liver mitochondrial ATP synthesis during warm ischemia and after reflow were studied separately in terms of the changes in oxidation (electron transfer system) and phosphorylation (H+-ATPase). Oxidative activity decreased significantly from the control value of 40 ± 0.9 (mean ± SEM, n = 5) to 31.5 ± 1.13 (nanoatoms oxygen consumed/min/mg protein) after 40 min of warm ischemia, while phosphorylative activity decreased significantly from the control value of 1.06 ± 0.12 to 0.42 ± 0.03 (μmole ATP hydrolyzed/min/mg protein) after 20 min of warm ischemia. During 120 min of reflow after 20 min of warm ischemia, the decreased phosphorylation activity recovered to 0.52 ± 0.01 concomitant with a recovery of intramitochondrial total adenine nucleotide and an increase in the ATP/ADP ratio, while oxidative activity decreased further to 23.9 ± 0.81. These results indicate that H+-ATPase is more vulnerable to warm ischemia than the electron transfer system, but that it is restored concomitant with the recovery of intramitochondrial adenine nucleotide content.

Lipid peroxidation in purified plasma membrane fractions of rat liver in relation to the hepatoxicity of carbon tetrachloride.

Preparations of rat liver sinusoidal plasma membrane have been tested for their ability to metabolize the hepatotoxin carbon tetrachloride (CCl4) to reactive free radicals in vitro and compared in this respect with standard preparations of rat liver microsomes. The sinusoidal plasma membranes were relatively free of endoplasmic reticulum-associated activities such as the enzymes of the cytochrome P450 system and glucose-6-phosphatase. CCl4 metabolism was measured as (i) covalent binding of [14C]-CCl4 to membrane protein, (ii) electron spin resonance spin-trapping of CCl3. radicals and (iii) CCl4-induced lipid peroxidation. By all of these tests, purified sinusoidal plasma membranes were found unable to metabolize CCl4. The fatty acid composition of the plasma membranes was almost identical to that of the microsomal preparation and both membrane fractions exhibited similar rates of the lipid peroxidation that was stimulated non-enzymically by gamma-radiation or incubation with ascorbate and iron. The absence of CCl4-induced lipid peroxidation in the plasma membranes seems to be due, therefore, to an absence of CCl4 activation rather than an inherent resistance to lipid peroxidation. We conclude that damage to the hepatocyte plasma membrane during CCl4 intoxication is not due to a significant local activation of CCl4 to CCl3. within that membrane.

The isolated perfused rat liver: Conceptual and practical considerations

The isolated perfused rat liver: Conceptual and practical considerations

Hepatocyte heterogeneity in glutamine and ammonia metabolism and the role of an intercellular glutamine cycle during ureogenesis in perfused rat liver.

1. The metabolism of glutamine and ammonia was studied in isolated perfused rat liver in relation to its dependence on the direction of perfusion by comparing the physiological antegrade (portal to caval vein) to the retrograde direction (caval to portal vein). 2. Added ammonium ions are mainly converted to urea in antegrade and to glutamine in retrograde perfusions. In the absence of added ammonia, endogenously arising ammonium ions are converted to glutamine in antegrade, but are washed out in retrograde perfusions. When glutamine synthetase is inhibited by methionine sulfoximine, direction of perfusion has no effect on urea synthesis from added or endogenous ammonia. 3. 14CO2 production from [1-14C]glutamine is higher in antegrade than in retrograde perfusions as a consequence of label dilution during retrograde perfusions. 4. The results are explained by substrate and enzyme activity gradients along the liver lobule under conditions of limiting ammonia supply for glutamine and urea synthesis, and they are consistent with a perivenous localization of glutamine synthetase and a predominantly periportal localization of glutaminase and urea synthesis. Further, the data indicate a predominantly periportal localization of endogenous ammonia production. The results provide a basis for an intercellular (as opposed to intracellular) glutamine cycling and its role under different metabolic conditions.

The energy-linked transhydrogenase in rat liver in relation to the reductive carboxylation of 2-oxoglutarate.

1 The energy-linked transhydrogenase reaction was studied in isolated mitochondria and in submitochondrial particles from rat liver. 2 The rate of the transhydrogenase reaction in intact mitochondria, estimated by measuring the rate of reduction of NADP+ with 3-hydroxybutyrate as hydrogen donor, was about 30 nmol · min−1· mg mitochondrial protein−1 at 25° C. This value was higher than that calculated from the rate of the energy-linked transhydrogenase measured in submitechondrial particles. From the ratio of the activities at 25° C and 37° C in submitochondrial particles and the rate at 25° C in intact mitochondria it was estimated that the rate of the transhydrogenase reaction in intact mitochondria at 37° C is about 80 nmol · min−1· mg protein−1. 3 In intact mitochondria the rate of reductive carboxylation of 2-oxoglutarate with 3-hydroxybutyrate as hydrogen donor was about 20 nmol · min−1· mg protein−1 at 37° C. The main product formed (> 95%) was citrate. 4 The concentration gradient of citrate across the mitochondrial membrane was the same during reductive carboxylation of 2-oxoglutarate as when citrate was added under non-flux conditions, indicating that transport of tricarboxylates does not limit citrate formation. 5 The activity of isocitrate dehydrogenase (NADP), measured in sonicated mitochondria in the direction of reductive carboxylation, was about 20 nmol · min−1· mg protein−1 at 37° C. 6 It is concluded that the rate of formation of citrate by reductive carboxylation of 2-oxoglutarate is limited by the activity of isocitrate dehydrogenase (NADP). However, the rate of citrate formation is sufficiently high to account for the transport of reducing equivalents needed for hydroxylation reactions in the extramitochondrial compartment in liver.

The influence of various bile salts and some cholephilic dyes on Na +, K +- and Mg 2+-activated ATPase of rat liver in relation to cholestatic effects

The influence of some agents which are known to affect bile fluid formation in the rat was studied on Na+, K+, Mg2+, and Mg2+-activated ATPase of rat livers. A microsomal membrane preparation containing membrane parts of both the sinusoidal and canalicular portions of the liver plasma membranes was used. The substances studied included taurodeoxycholate, taurochenodeoxycholate, taurolithocholate, taurocholate, and taurodehydrocholate, some non-bile salt choleretics such as ouabain, phenolphthalein-glucuronide, ethacrynic acid, and its glutathione derivative in addition to some dyes with mixed choleretic and cholestatic properties such as sulfobromophthalein (BSP), BSP-glutathione, indocyanine green (ICG), rose bengal (RB), and dibromosulphthalein (DBSP). In the bile salt group all agents except taurodehydrocholate were inhibitors of Mg2+ ATPase at concentrations ranging from 10−4–10−3 m. Only taurolithocholate at about 10−4 m showed specific inhibition of the Na+, K+-activated part of the enzymes, a result which was also observed for the cardiac glycosides ouabain and K-strophanthoside. Ethacrynic acid and phenolphthalein-glucuronide inhibited Mg2+ ATPase at about 10−3 m; inhibition of the Na+, K+ ATPase only slightly contributed to the effect on total ATPase activity. The dyes RB, ICG, BSP, and DBSP exhibited strong ATPase inhibition at concentrations of 10−5 (RB) and 10−4 m (ICG, BSP, and DBSP); only in the case of rose bengal could a specific effect on Na+, K+-activated ATPase be concluded (I50 = 1.6 × 10−6 m). Conjugation with glutathione strongly reduced the effect of ethacrynic acid and BSP on rat liver ATPase. DBSP and phenolphthalein-glucuronide induced a slowly increasing choleresis after injection in vivo in the rat with no fixed relation between extra bile blow and biliary output of these agents. This choleretic response can be explained by a resultant of a transient inhibitory influence and a stimulatory effect on bile production which is possibly due to the osmotic activity of the excreted compounds. It is shown that these agents reach levels in bile which are high enough to produce considerable inhibition of Mg2+-activated ATPase at canalicular sites, an effect which might be related to this inhibitory effect on bile production. Ethacrynic acid which, after injection in vivo, was mainly excreted in bile as the glutathione derivative, and ouabain administered to isolated perfused rat liver, produced a choleretic response in time, which seemed closely related to the biliary excretion pattern. The observation that ouabain concentrations in bile exceed the half inhibitory concentrations of Na+, K+ ATPase about 150 times, while it induces a profound choleresis, raises doubts about the proposed role of canalicular Na+, K+ ATPase in the formation of bile fluid in the rat.

Canalicular bile formation in the isolated perfused rat liver.

Canalicular bile formation in the isolated perfused rat liver.

Rate of RNA turnover in rat liver in relation to intake of protein

The effect of dietary intake of protein on the turnover of liver RNA has been measured in rats by observing the rate of loss of label from liver ribosomal RNA over a period of several days after injection of 3H-labeled orotic acid. Rats receiving a normal intake of protein showed fractional rates of RNA synthesis and degradation of about 20–25% daily. When rats were fed a diet free of protein, RNA breakdown was at first accelerated to over 40% per day. However, after 2 days on the protein-free diet the fractional rate of degradation fell to about 15% daily, and the rate of RNA synthesis to an even lower level, so that animals on this diet showed a continuous reduction in the RNA content of their livers. On the basis of the present and earlier studies, it is suggested that RNA turnover is regulated through changes in the population of free ribosomal subunits in the liver cytoplasm, the abundance of subunits being affected by amino acid supply.

Intermediary carbohydrate metabolism in injured rat liver in relation to heat production. In: Energy metabolism in trauma.

Intermediary carbohydrate metabolism in injured rat liver in relation to heat production. In: Energy metabolism in trauma.

Protein metabolism among lobes of the rat liver in relation to site of radioisotope injection.

SummaryProtein metabolism among rat liver lobes was studied by leucine-3H injections coupled with liquid scintillation spectrometry of TCA-tungstate soluble and insoluble fractions. All liver lobes appeared to metabolize protein in identical fashion when the label was injected in the external jugular vein. On a per milligram of wet weight basis, the lobes exhibited similar values of radioactivity at the various experimental times. When this data was converted to total radioactivity per lobe a positive correlation was revealed between total lobe radioactivity and lobe weight. However, when the radioisotope was injected directly into the spleen, it was the right side of the liver which contained most radioactivity 15 min later. Whereas leucine-3H injection into the lumen of the jejunum resulted in lobes of the left side having most radioactivity 15 min later. This was interpreted as a crossing-over of streamlined blood flow in the rat portal vein under these experimental conditions.The authors gratefully ac...

Development of guanase and xanthine oxidase in rat liver.

SummaryActivities of the metabolically related rat liver enzymes, guanase and xanthine oxidase, increase markedly from birth to maturity. Temporal difference in the increases suggests that they are signaled differently.

THE DEOXYRIBONUCLEASE OF RAT LIVER IN RELATION TO THE ISOLATION OF DEOXYRIBONUCLEOPROTEIN

THE DEOXYRIBONUCLEASE OF RAT LIVER IN RELATION TO THE ISOLATION OF DEOXYRIBONUCLEOPROTEIN

Phosphatase activity in rat liver in relation to cells and mitochondria

The alkaline phosphatase activity per cell was not altered by protein depletion of the livers of rats caused by feeding a protein-free diet but per gram of tissue the activity and the number of cells were doubled. The acid phosphatase activity in the livers of rats fed the protein-free diet although unchanged per gram was only 50 per cent as great per cell as in the livers of rats fed the Fox Food Blox diet. Protein depletion decreased the number of mitochondria per cell, but greatly increased the alkaline and acid phosphatase activity per mitochondrion.