Effect of fatigue on nucleic acid metabolism in the regenerating liver of partially hepatectomized rats

Summary A considerable fatigue attained by prolonged swimming caused a marked reduction of the intensity of nucleic acid renewal in the regenerating rat liver 24 hours after partial hepatectomy (RNA by 28%, DNA by 48%) without affecting the content of these acids in the organ investigated. A model is suggested for studying the efficancy of low doses of ionizing radiation, i.e., reduction of nucleic acid synthesis in the regenerating liver of partially hepatectomized rats, resulting from prolonged fatigue. (Presented by Active Member AMN SSSR A. V. Lebedinskii) Translated from Byulleten' éksperimental'noi Biologii i Meditsiny, Vol. 56, No. 11, pp. 79–81, November, 1963.     

Amino acid metabolism in the isolated perfused rat liver

1. Rat livers have been perfused with homologous blood and the distribution of (15)N from labelled amino acids added to the perfusate studied.2. Each of the amino acids added, aspartate, alanine, glycine, and glutamate (unlabelled) were rapidly removed from the perfusate. Glutamate was formed from added aspartate (but not from added alanine or glycine) by transamination in the perfusate plasma; the perfusate concentration of no other amino acid was affected by addition of any of the acids investigated.3. Urea output was increased by addition of aspartate, increase in output after addition of alanine or glycine was not significant.4. After addition of labelled aspartate, alanine or glycine an increase in isotope ratio was detected in urea, ammonia, glutamine, aspartate and alanine in the perfusate and, in some experiments, in the liver. After addition of alanine an increase was also detected in lysine, tyrosine, phenylalanine, methionine, proline, tryptophan and threonine+serine (analysed together).     

Bile acid transport and metabolism in rat liver slices

To further characterise precision-cut liver slices from 34- to 40-day-old male rats as an in vitro model for bile acid (BA) metabolism and transport, the effect of the primary BAs cholic (CA, 5 microM) and chenodeoxycholic acid (CDCA, 0.15 and 0.75 microM) as well as of the therapeutically used tauroursodeoxycholic acid (T-UDCA, 5 microM) on BA profiles was investigated. After 4 h incubation in 5 ml Krebs-Henseleit buffer (KHB) 26 individual BAs were determined in slices (50 mg liver/5 ml KHB) and medium by HPLC with postcolumn derivatisation and fluorescence detection. In control incubations, mean total BA concentrations were 5.09 nmol/50 mg liver (101.80 nmol/g liver) in slices and 25.71 nmol/5 ml KHB, among them 72% taurine-(T-), 22% glycine-(G-) conjugated and 6% free BAs in tissue and medium. The main BAs were beta-muricholic (beta-MCA and conjugates) and cholic acids (CA and conjugates) in tissue and medium. The following results were obtained after addition of CDCA, CA, and T-UDCA, respectively, to the KHB. The toxic CDCA was quantitatively converted mainly to T-UDCA and taurohyodeoxycholic (T-HDCA) acid. CA was conjugated in equal shares to T- and G-CA, whereas T-UDCA was enriched in slices and hydroxylated half to T-beta-MCA, which is the main BA in rats. In conclusion, rat liver slices are highly effective not only in uptake, conjugation and excretion of BAs but also in conversion of strong detergent into less toxic BAs.     

Effect of carbon tetrachloride on RNA metabolism in the rat liver

The effect of systematic administration of carbon tetrachloride (CCl₄) to rats on the RNA content in the liver and the intensity of incorporation of the labeled precursor (uridine-H³) into it was investigated. Comparison of the results of morphological and biochemical studies revealed two consecutive stages of the toxic process, terminating in the formation of septal fibrosis. The sharpest changes in rapid RNA turnover in the rat liver were observed during the first 3 months of action of the toxic agent. The disturbance of metabolism also was reflected in a lowered RNA level and changes in the nucleo-cytoplasmic ratio in the tissue of the affected liver.Laboratory of Biochemistry and of Chemical Carcinogenic Agents, N. N. Petrov Research Institute of Oncology, Ministry of Health of the USSR. (Presented by Academician of the Academy of Medical Sciences of the USSR A. I. Serebrov.) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 81, No. 5, pp. 543–545, May, 1976     

The effect of ionizing radiation on the nucleic acid content of rat liver mitochondria

Summary The object of study was the influence of high doses of ionizing radiation (1500–2000 r) on the RNA content of mitochondria of the liver in albino rats. Mitochondria were isolated 2 h after the irradiation of animals. A significant increase in the RNA level was discovered in comparison to the mitochondria of the liver in healthy animals (by 88% on the average).Presented by I. R. Petrov, Active Member of the Academy of Medical Sciences USSR Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 61, No. 1, pp. 51–52, January, 1966     

Age-related changes of long-chain fatty acid metabolism in rat liver

Palmitate oxidation activity and the activities of several enzymes involved in long-chain fatty acid metabolism were examined in the liver of young adult (2-month-old) and senescent (32-month-old) female rats. Palmitate oxidation activity in rat liver mitochondria showed age-related decrease, as judged by the rates of both 14CO2 production and formation of radioactive acid-soluble products from [1-14C]palmitate. In addition, long-chain acyl-coenzyme A synthetase activity was found to be decreased in liver mitochondria and increased in liver microsomes in senescent rats. These results suggest that, in the rat liver, preferential channeling of long-chain fatty acids through the triacylglycerol synthetic pathway may increase with age, and as a result, energy production by their oxidation may decrease.     

Effect of maternal protein restriction on liver metabolism in rat offspring

Consequences of gestational protein restriction (GPR) on liver metabolism in rat offspring were investigated. Pregnant dams were divided into groups: normal (NP, 17 % casein) or low-protein diet (LP, 6 % casein). Livers were collected from 30-day-old offspring (d30) for analysis or isolation of mitochondria. At d30, hepatic and muscle glycogen was increased in LP group. Mitochondrial swelling and oxygen uptake (recorded with a Clark-type electrode) were significantly reduced in NP female and LP pups. Thiobarbituric acid reactive substances production was lower in females (NP or LP), suggesting significant inhibition of lipid peroxidation. Measurement of mitochondrial respiration (states 3 and 4 stimulated by succinate) showed a higher ADP/O ratio in LP pups, particularly females, suggesting higher phosphorylation efficiency. In the 1st month of life, under our experimental conditions, GPR protects liver mitochondria against oxidative stress and females seem to be more resistant or more suitable for survival.     

Acute effects of acidosis on protein and amino acid metabolism in perfused rat liver

Acidosis is frequently associated with protein wasting and derangements in amino acid metabolism. As its effect on protein metabolism is significantly modulated by other abnormal metabolic conditions caused by specific illnesses, it is difficult to separate out the effects on protein metabolism solely due to acidosis. The aim of the present study was to evaluate, using a model of isolated perfused rat liver, the direct response of hepatic tissue to acidosis. We have compared hepatic response to perfusion with a solution of pH 7.2 and 7.4 (controls). Parameters of protein and amino acid metabolism were measured using both recirculation and single-pass technique with 4,5-[3H]leucine, [1-14C]leucine and [1-14C]ketoisocaproate (ketoleucine) as tracers and on the basis of difference of amino acid levels in perfusion solution at the beginning and end of perfusion. In liver perfused with a solution of pH 7.2, we observed higher rates of proteolysis, protein synthesis, amino acid utilization and urea production. Furthermore, the liver perfused with a solution of pH 7.2 released a higher amount of proteins to perfusate than the liver perfused with a solution of pH 7.4. Enhanced decarboxylation of ketoisocaproate in liver perfused by a solution of a lower pH indicates increased catabolism of branched-chain amino acids (leucine, valine and isoleucine), decreased reamination of branched-chain keto acids to corresponding essential amino acids and increased ketogenesis from leucine.     

Chromosome aberrations in rat liver cells and bone marrow cells following treatment in vivo with mitomycin C

The clastogenic potential of mitomycin C (MMC) was studied inrat liver cells and bone marrow cells. Male Sprague-Dawley ratswere partially hepatectomized and treated wtih a single i.p.dose of MMC (3.5 mg/kg body weight) 7 or 24 h after the operation.Non-hepatectomized rats were also treated with the same doseof MMC 7 or 24 h after the mutagenic treatment; liver and bonemarrow cells were isolated from hepatectomized rats (31 h afterthe operation) and bone marrow cells only from non-hepatectomizedanimals. The results show that, if MMC was administered 7 hbefore the isolation of cells, the induction was more efficientin liver cells than in bone marrow cells. At this sampling time,there was no consistent difference between the frequencies observedin bone marrow cells from hepatectomized and non-hepatectomizedrats. An increase was observed in both tissues 24 h after themutagenic treatment. At this sampling time, the effect was significantlyhigher in the bone marrow cells from non-hepatectomized animalsthan in the liver cells and bone marrow cells from hepatectomizedanimals. No significant difference between the two cell typesfrom hepatectomized rats was observed. Different factors relatedto the cytostatic properties of MMC and/or to cell kineticsin the two cell types, probably affected by the surgical operation,may account for the differences in the yield of chromosomaldamage. ¹To whom correspondence should be addressed     

Effect of factors causing excitation and inribition on polyphosphoinositide metabolism of the rat liver

The rate of incorporation of radioactive phosphate into the polyphosphoinositide (PPI) fraction is about 10 times greater than into other phospholipids (PL) of the normal rat liver. Rapid postmortem changes in the PPI content in the liver were found. During exposure to the various factors used, the only PL fraction in which changes were found was the PPI fraction. Changes in the content and also in the intensity of metabolism of PPI in the liver were similar in direction during exposure to these factors to those in the brain. The PPI fractions are the most labile PL fractions in the liver.     

丝裂霉素C对辐射损伤小鼠胸腺细胞的影响

目的：在选择辐射损伤小鼠胸腺细胞适宜剂量的基础上，观察丝裂霉素C（MMC）对辐射损伤小鼠胸腺细胞自发掺入的影响。 方法： 流式细胞仪检测小鼠胸腺细胞周期，选择辐射剂量；用［³H］-TdR掺入法研究MMC对辐射损伤小鼠胸腺细胞的作用。 结果： 选择用γ-射线1.5 Gy全身照射小鼠，建立辐射损伤模型。 0.04 μg/kg MMC对辐射损伤有拮抗作用，表现为0.04 μg/kg MMC+1.5 Gy照射组胸腺细胞自发掺入率明显高于生理盐水+1.5 Gy照射组。 结论： 一定剂量MMC可拮抗辐射损伤小鼠胸腺细胞。