RNA Content Of Liver Research Articles

Hepatic protein synthesis and serum aminoacid levels during liver regeneration in young and old malnourished rats

The aim of the present study was to measure protein synthesis in regenerating liver and to evaluate the impact of malnutrition in young and old rats. Two groups of male Wistar rats were used: young rats (4 months old) and old rats (18 months old). The rats were allocated to malnutrition or ordinary food intake for 1 week. Half of each group was sham-operated and the other was partially hepatectomized 2 days before the end of diet manipulation. Hepatic protein synthesis was significantly increased in all hepatectomized groups compared with their respective sham group: young well-nourished hepatectomized rats, 44%; young malnourished hepatectomized rats, 55%; old well-nourished hepatectomized rats, 47%; and old malnurished hepatectomized rats only 21%. Hepatic DNA content was unchanged in all groups and liver RNA content was higher in young malnourished hepatectomized rats (21%, P < 0.05). Serum total amino acid concentration did not change in young well-nourished hepatectomized and young malnourished hepatectomized rats. This value did not show significant changes between old well-nourished hepatectomized and old well-nourished sham, but it increased 14% ( P < 0.05) in old malnourished hepatectomized. It was concluded that (a) regeneration is not impaired by malnutrition in young rats and may even be better than in rats eating a normal diet, and (b) the deleterious effect of aging is revealed once old animals are exposed to malnutrition. It is manifested in the decreased rete of hepatic protein synthesis observed in old malnourished hepatectomized rats and in the augmentation of total serum amino acid concentration, where the hypercatabolism induced by hepatectomy is significantly greater.

Effect of Caralluma tuberculata on the cytological and biochemical changes induced by cyclophosphamide in mice

Treatment with Caralluma tuberculata extract induced complex biochemical and cytological changes in mice. Its cytotoxicity in the bone marrow cells of mice was comparable with that of the standard drug cyclophosphamide (CP); however, unlike CP, C. tuberculata was not clastogenic (as shown by the micronucleus assay). A dose-dependent decrease in the RNA content of liver and testes was produced by C. tuberculata treatment whereas there was no effect on the content of nucleic acid and protein in the brain. In the extract-treated animals there was a significant and dose-dependent increase in the DNA content of the liver, with a negligible effect on the protein content. Combined treatment with C. tuberculata and CP showed that C. tuberculata diminished the effect of CP on DNA levels; however, RNA levels were further suppressed, resulting in increased cytotoxicity. Pretreatment with C. tuberculata extract significantly reduced the clastogenicity of CP. These results indicated the involvement of different phytoconstituents acting by different routes.

Tumor and host response to arginine and branched chain amino acid-enriched total parenteral nutrition. A study involving Walker 256 carcinosarcoma-bearing rats.

The metabolic effects of total parenteral nutrition (TPN) solutions containing different profiles of individual amino acids were investigated in the rats bearing Walker 256 carcinosarcoma. The rats were subcutaneously inoculated with 10(7) tumor cells and 6 days later were continuously infused intravenously for 8 days with three different TPN solutions. The experimental and control solutions were composed of high concentrations of branched chain amino acids (BCAA) and arginine (high Arg + BCAA TPN), high concentrations of BCAA (high BCAA TPN) and regular amino acids (regular TPN), respectively, and were isonitrogenous, isocaloric, and isovolemic. Rats receiving subcutaneous injection of saline rather than tumor cells received high Arg + BCAA TPN as pair-fed controls. The flooding dose method of 14C-leucine was used for the analysis of protein synthesis. With the feeding of high Arg + BCAA TPN, the tumor-bearing rats revealed a smaller increase of tumor volume and lower tumor fractional rates of growth (Kg) and synthesis (Ks) as well as protein synthesis (PS), compared with the high BCAA TPN and regular TPN in tumor-bearing rats. There were no significant differences of Ks and PS in liver and muscle between TPN groups, whereas tumor-bearing rats infused with high Arg + BCAA TPN displayed higher levels of whole-body Ks and PS than other TPN groups in tumor-bearing rats and pair-fed nontumorous rats. Except for liver RNA content which showed a lower level in tumor-bearing rats with high Arg + BCAA TPN, no other differences of DNA and RNA contents were found in tumor, liver, and muscle of the different TPN groups. The current results indicate that individual amino acids can influence tumor growth and protein metabolism, and that arginine, in combination with BCAA, may reduce tumor growth through a reduction in protein synthesis.

Effect of age and restricted feeding on polypeptide chain assembly kinetics in liver protein synthesis in vivo

Polypeptide assembly rates during in vivo hepatic protein synthesis were studied as a function of age and restricted feeding in male rats. With ageing the time to assemble the average peptide in the liver of fully-fed rats significantly increased. In young rats maintained on a restricted feeding regime known to retard ageing, the time to assemble the average polypeptide was increased 2.5 times. With ageing the rate of peptide elongation increased so that at 2 years of age the underfed animals assembled peptides at a significantly faster rate than their age-matched controls. The rate of elongation of peptides during hepatic protein synthesis was shown to be directly dependent upon circulating T 3 levels rather than the dietary status of the animal. On refeeding young diet restricted rats, polypeptide assembly kinetics did not immediately return to control values although the rate of protein synthesis was significantly increased. Total liver RNA content increased significantly in refed animasl allowing for a greater rate of chain intiation to offset the slow rate of chain elongation. A period of 28 days of ad libitum feeding was required before assembly kinetics returned to control values and is probably indicative of a persistent impaired monodeiodination of T 4 to T 3.

Interaction between ovine growth hormone and triiodo-L-thyronine on metabolic reserves of rainbow trout,Salmo gairdneri

Rainbow trout (Salmo gairneri) were given slow-release coconut oil implants which contained triiodo-L-thyronine (T3) and were subsequently administered ovine growth hormone (oGH) (either 0.24 or 2.5 μg/g body weight) or saline every seventh day for four injections. The purpose of the study was to examine the interactions between oGH and T3 on several aspects of the metabolism in rainbow trout.Trout treated with T3 alone had higher carcass water content, lower liver glycogen, higher plasma T3 levels and lower plasma cholesterol, triglyceride and protein levels compared with the controls implanted with coconut oil implants alone. Trout treated with oGH alone had higher condition factors, lowered carcass total lipid content, elevated liver lipid and RNA content, and elevated plasma T3 and L-thyroxine (T4) levels compared with the coconut oil-implanted and saline-injected controls. Trout treated with T3 and oGH had lower liver glycogen content, higher plasma T3 and fatty acid levels and lower plasma T4, cholesterol and triglyceride levels compared with the controls given coconut oil implants and saline injections alone. There were no apparent effects of either hormone alone or in combination on liver: body mass ratios, liver DNA content, liver RNA:DNA ratios, liver RNA:protein ratios, liver protein:DNA ratios and liver protein content.The data suggest an interaction between oGH and T3 as regards the regulation of condition factor, carcass water content, carcass and liver total lipid content, liver RNA content, plasma fatty acid and plasma protein content.

Effects of experimentally induced nephrosis on protein synthesis in rat liver.

A nephrotic syndrome was experimentally induced in rats by a single intravenous injection of aminonucleoside of puromycin. Experimental animals were studied 8 days after the injection, at which time they exhibited marked proteinuria and hypoalbuminemia compared with control animals. The experimental animals also exhibited alterations in protein synthesis in liver as evidenced by a marked increase in the rate of albumin synthesis relative to total hepatic protein synthesis, changes in the relative concentrations of several plasma proteins, an increased protein content of plasma, an increased liver weight relative to body weight, and an increased RNA content of liver. Perfused liver preparations derived from nephrotic rats exhibited an increased release of albumin and other secretory proteins compared with control preparations. In contrast, there was no difference in the rate of synthesis of nonexported proteins between the two groups. The elevation in the relative rate of albumin synthesis was accompanied by a relative increase of the same magnitude in albumin mRNA. Furthermore, the relative amounts of several other mRNAs, including those coding for beta-fibrinogen, haptoglobin, metallothionein II, and two unidentified proteins, were increased, whereas the amount of mRNA coding for alpha 1-acid glycoprotein was decreased in livers of nephrotic rats compared to controls. These results indicate that nephrosis leads to marked alterations in the synthesis of albumin and other plasma proteins. Mechanisms responsible for these alterations include changes in the relative abundance of specific mRNAs and an increase in total cellular RNA.

In vivo DNA synthesis in the dietary restricted long-lived rat

Male CFY Sprague-Dawley rats maintained at 50% growth rate of ad libitum fed, age-matched control animals showed a 42% extension in maximum lifespan and an increase in the overall doubling time of the rate of mortality from 102 days to 203 days. The slower growth rate of animals on the restricted diet was reflected in lower DNA, RNA, and protein c content of liver, kidney and heart with age. DNA synthesis in vivo measured by the incorporation of 3H-thymidine was severely inhibited in liver, kidney, heart, and abdominal skin, particularly during the first six months of life. The developmental peak in DNA synthesis observed in liver and kidney of ad libitum fed animals before 100 days of age was completely inhibited. No effect of restricted feeding on DNA synthesis in the small intestine was observed; however, DNA synthesis was higher in thymic tissue from the experimental animals. A decrease in RNA content of liver, kidney, and heart preceded any change in protein or DNA in animals subjected to restricted feeding. The capacity for protein synthesis (RNA/DNA ratio) was decreased by restricted feeding and was associated with a reduced protein/DNA ratio indicative of reduced cell size during the first six months of life. The translational activity per ribosome (protein/RNA ratio) was not disturbed by undernutrition in any of the tissues studied.

The effect of thyroid hormones and temperature on protein and nucleic acid contents of liver and muscle of Sarotherodon mossambica

The effect of thyroid hormones (T3 and T4) and their relation to temperature and age was observed in liver and muscle protein and nucleic acids of Sarotherodon mossambica (tilapia). Single injections of both T3 and T4 (0.25–2.0 μg/g body wt) induced an increase in the protein and RNA content of liver and muscle. No effect on the DNA was observed. The effect of these hormones was dose dependent, and while the lower doses (0.25–1.0 μg/g) increased the protein and RNA, the higher dose (2.0 μg/g) elicited catabolic effects in both tissues. Temperature (15–30°) of the ambient water influenced the effect of thyroid hormones in both tissues. However, T4 became catabolic at high temperature (30°). Thyroid hormones required to increase the weight gain and RNA and protein synthesis of tilapia fry increased with increase in age. Thus, for 1-week-old tilapia, 10 μg/100 ml of T4 in the aquarium water is the maximum concentration, while for 3-week-old tilapia, this dose is 25 μg/100 ml. The effect of thyroid hormones on the increase of protein and nucleic acids of liver and muscle was observed only in tilapia of up to 40 g. Fish of 230 g showed no response in this respect. The results are discussed in the light of earlier reports on thyroid hormones and fish growth.

Biochemical and toxicological effects of combined exposure to 1,1,1-trichloroethane and trichloroethylene on rat liver and brain.

1. Inhalation exposure of adult male rats to a mixture of 1,1,1-trichloroethane (500 p.p.m.) and trichloroethylene (200 p.p.m.) for four days 6 h daily resulted in an accumulation of 1,1,1-trichloroethane in perirenal fat. Further exposure on the fifth day caused a rapid increase in various organ contents of both solvents with secondary depression of brain RNA. 2. The four-day exposure doubled the RNA content of liver and caused a slight decline in the concentrations of glutathione in liver. 3. The amount of cytochrome P-450 in liver was increased, as well as the overall mono-oxygenase activity, measured with styrene as substrate. During continuing treatment on the fifth day, styrene mono-oxygenase activity decreased, the activity after 6 h being only about 50% of that at the beginning of the fifth day of exposure. 4. UDP-glucuronosyl transferase activity (measured in digitonin-activated microsomes) was doubled by the four-day combined exposure to 1,1,1-trichloroethane and trichloroethylene. 5. The changes during the fifth day of exposure, e.g. rapid increase in the concentrations of solvents in organs, the detection of trichloroethylene in tissues and depression of mono-oxygenase activity, obviously also occurred during the exposures on days 1 to 4 and reverted during each post-exposure period.

Enhancing and inhibitory effects of some stilbene and steroid compounds on induction of hepatoma in rats fed 3'-methyl-4-(dimethylamino)azobenzene.

Examinations were made on substances that enhance or inhibit the induction of hepatoma in rats previously fed 3'-methyl-4-(dimethylamino)azobenzene (3'-Me-DAB) for a brief period. The substances tested were stilbene, 4-nitrostilbene, 4,4'-dihydroxystilbene, diethylstilbestrol, 17beta-estradiol, and methyltestosterone. Male Donryu rats were fed 0.5 g of 3'-Me-DAB by being maintained on a diet containing 0.06% 3'-Me-DAB, and then they were fed 0.25 or 0.5 g of a test substance with the basal diet. Comparison of the development and yield of hepatomas indicated that 4-nitrostilbene and methyltestosterone had an activity of enhancing 3'-Me-DAB carcinogenesis, whereas diethylstilbestrol and 17beta-estradiol had an activity to retard it. Other substances showed no such activities. The enhancement by 4-nitrostilbene and inhibition by diethylstilbestrol of 3'-Me-DAB carcinogenesis was correlated with their effect on liver nucleic acid metabolism. Feeding of 4-nitrostilbene caused a selective inhibition of Mn2+-(NH4)2SO4-activated RNA polymerase activity of liver nuclei and reduced liver RNA content. The deleterious alteration of liver RNA metabolism was followed by the enhancement in the incorporation of ip-injected 3H-thymidine into DNA of liver nuclei. On the other hand, feeding of diethylstilbestrol increased tissue RNA content without effect on RNA polymerase activity of liver nuclei, and had an activity of increasing the incorporation of 3H-thymidine into DNA. The possible implication of these results with regard to the enhancement and inhibition of hepatocarcinogenesis is discussed.

Effects of protein deficiency on the biosynthesis and degradation of ribosomal RNA in rat liver.

Employing livers from rats fed on a protein-free diet for two weeks, the effects of protein deficiency on both biosynthesis and degradation of rRNA were investigated and the following results were obtained. 1. Protein deficiency led to a decrease of total liver RNA content per DNA to about 80% of that in normal rat liver. 2. From the kinetics of rRNA labelling with [14C]orotic acid in vivo, the half-lives of cytoplasmic rRNA's of normal and protein-deficient rat livers were determined to be 6.2 and 5.1 days, respectively. Furthermore, considering the pool size of rRNA in rat liver, the turnover rate of cytoplasmic rRNA was calculated to be 0.212 pmole/min/mg of nuclear DNA in normal rats and 0.240 pmole/min/mg of nuclear DNA in protein-deficient rats. 3. From the electrophoretic patterns of nucleolar RNA's of both groups of rat livers labeled with [14C]orotic acid, the time courses of the specific activities of nucleolar 45S, 32S, and 28S rRNA's were analysed and the half-life of each nucleolar RNA in both groups of rat livers was determined. Nucleolar 45S, 32S, and 28S RNA's had half-lives of 6.0, 15.9, and 26.5 min in normal rats, respectively, and 5.5, 19.4, and 22.9 min in protein-deficient rats, respectively Considering the pool size of each nucleolar RNA obtained from the leectrophoretic pattern, the turnover rates of 45S, 32S, and 28S RNA's were calculated to be the same, i.e., o.189 pmoles/min/mg of nuclear DNA, in normal rat liver and 0.372, 0.372, and 0.358 pmoles/min/mg of nuclear DNA in protein-deficient rat liver, respectively. 4. These results indicate that protein deficiency increased both the rate of degradation of cytoplasmic rRNA and that of nucleolar rRNA synthesis in rat liver. While in normal rat liver the rates of rRNA synthesis and degradation were rather similar, the rate of rRNA synthesis in protein-deficient rats was about 1.5 times higher than that of its degradation. Therefore, the decrease of total liver RNA content in protein deficiency might be accounted for by stimulated degradation of rRNA in the nucleus. 5. The activities of RNase in nuclear fractions of both groups of rat livers were compared. Both activities of nuclear acid RNase and especially that of the free form of alkaline RNase in protein-deficient rat liver were higher than those in normal rat liver.

Effect of carbon tetrachloride on RNA metabolism in the rat liver

The effect of chronic CCl4 treatment on both the liver RNA content and 3H-uridine incorporation was studied. Comparison of morphologic and biochemical parameters allowed to define two successive stages of toxic process resulting in septal fibrosis. The most significant changes in the rat liver rapid RNA turnover were observed during the first 3 months of the toxic agent action. The metabolic disturbances were also manifest in both decreased RNA content and changes of nuclear-cytoplasmic interrelationships in the damage liver tissue.

Total human body protein synthesis in relation to protein requirements at various ages.

THE intensity of body and tissue protein metabolism per kg declines with increased adult body size in mammals1. This fall parallels a similar progressive decline in the intensity of energy metabolism2–4. It has also been concluded that protein metabolism per unit of body weight is about four to five times faster in young rats than in adult man1; this pattern of change extends to cellular and subcellular aspects of protein metabolism, such as plasma albumin synthesis, liver RNA content and enzyme activity1,5. Similarly, the rate of protein synthesis per kg total body weight declines during growth and development within a species, such as the rat6. This parameter again parallels the reduction in the intensity of energy metabolism which occurs during the growth period3.

Stimulation of hepatic RNA synthesis in dwarf mice by ovine prolactin

Dwarf mice ( dw dw ) have a lower liver RNA to DNA ratio compared to their congenic littermates (+/?). Injection of ovine prolactin into dwarf mice increases the total RNA content of liver. Dwarf mice appear to incorporate less [ 3H]uridine into total hepatic RNA after pulse injection than normal mice. Prolactin first stimulates the synthesis of guanine-rich then uridine-rich RNA of the whole liver homogenate. In liver nuclei, incorporation of [ 14C]guanine into RNA after correction for the acid-soluble pool is significantly increased during the first 3 days of treatment, whereas [ 3H]uridine incorporation rises substantially only after 4–5 days of treatment. In mitochondria, which incorporate labeled precursors into RNA, prolactin stimulates mainly the synthesis of uridine-rich RNA. A single dose of prolactin ( 10 I.U. 7 g body weight) stimulates the assembly of ribosomes into polyribosomes. Total amounts of ribosomes and polyribosomes continuously increase during the 5 days of prolactin treatment.

Interrelations of Diet-induced Changes in Hexosemonophosphate Shunt Dehydrogenases with RNA Metabolism in Rat Liver Slices ,

The relationship of changes in hexosemonophosphate shunt dehydrogenase activity to RNA metabolism in response to fasting and fasting-refeeding a high carbohydrate protein-free diet or a high protein carbohydrate-free diet was investigated in rat liver slices. Starvation for 48 hours did not change hexosemonophosphate shunt dehydrogenase activity but resulted in a significant decrease in liver RNA content. When a high carbohydrate protein-free diet was refed for 48 hours, the dehydrogenease activity did not change and the pattern of incorporation of glucose-1, glucose-2, and glucose-6-14C into acid-soluble nucleotides indicated relatively little use of the oxidative part of the hexosemonophosphate shunt pathway for ribose synthesis. While the RNA content of the liver under this regimen remained unchanged from fasting levels, the rate of incorporation of radioactive precursors into RNA was restored to control untreated values.When a high protein carbohydrate-free diet was refed, increased levels of the hexosemonophosphate shunt dehydrogenase activity were observed. The pattern of incorporation of glucose carbon into acid-soluble nucleotides under these conditions suggested an increase in ribose formation by way of the oxidative portion of the hexosemonophosphate shunt dehydrogenase pathway. The nucleic acid content of the liver of this group was not different from that of control untreated rats. The results are discussed in relation to the dietary control of alternative pathways of pentose production for nucleic acid synthesis.

Effect of riboflavine deficiency on nucleic acid metabolism of liver in the rat.

1. The effect of riboflavine deficiency on liver ribonuclease activity, RNA and DNA content, and32P incorporation into RNA and DNA has been studied in rats maintained on a 16% protein diet, a protein-free diet and on a protein-free diet subsequently replaced with a 40% protein diet.2. Rats maintained on a riboflavine-deficient diet for 45 days showed decreased incorporation of32P into liver RNA but no effect on the RNA content of liver. The concentration of DNA in liver and33P incorporation into it remained unaffected. After a deficiency period of 70 days, both the RNA and DNA contents of liver were found to be decreased. When the riboflavine-deficient or control rats were given the protein diet for 30 days and then a proteinfree diet for 15 days, the RNA content of their livers decreased, while the liver DNA content was increased. Repletion with a 40% protein diet restored the RNA and DNA content in both control and riboflavine-deficient rats.3. Liver ribonuclease activity was decreased after a deficiency period of 45 days, whereas it was increased after a deficiency period of 70 days.4. A correlation between liver RNA level and liver ribonuclease activity in riboflavine deficiency is suggested.

Systematic Oscillations in the Metabolism of Orotic Acid in the Rat Adapted to a Controlled Feeding Schedule

Orotic acid labeled with 14C in the 7-, 2- or 6-position has been used to obtain information on its metabolism in the rat adapted to a 48-hour cycle of 8 hours of feeding and 40 hours of fasting. The conversion of orotic acid to uridine monophosphate (UMP) did not vary with the nutritional state of the rat throughout the cycle. However, the further metabolism of UMP derived from injected ring-labeled orotic acid, as determined by its incorporation into liver RNA and degradation to CO2, did show cyclic variations, corresponding with a cyclic variation of the total liver RNA content. The increase in degradation to CO2 of UMP derived from injected orotic acid in the fasting period of the cycle suggests an increase in catabolic enzymic activity. A simple and efficient method for collecting and determining expired 14CO2 is described.

Studies on the nature and specificity of the induction of several adaptive enzymes responsive to cortisol

IT IS becoming increasingly evident that the complex processes of growth and differentiation have control mechanisms capable of coordinating the biosynthetic and degradative pathways of metabolism. There are many reports indicating that an increased rate of synthesis of certain enzymes is one of the biochemical effects elicited by the glucocorticoids.(r*s) Part of the regulatory role that hormones play in the metabolism of mammalian cells probably involves alterations in the activities of certain enzymes.@*4) Although the biochemical significance of these observations is evident, as is emphasized by this symposium, it is difficult to evaluate the functional importance of these enzymes in relation to physiological responses to glucocorticoids. Many current investigations are concerned with the question, “How do glucocorticoids stimulate enzyme synthesis ?” Several studies have related treatment with moderate doses of glucocorticoids to slight increases in the RNA content of liver.@-7) The inhibitory effect of actinomycin D on the response of the adaptive enzymes implies a requirement for new templates of RNA in enzyme induction.(s) Garren and Howell@) observed that cortisone was effective in stimulating the uptake of CrJ-erotic acid into nuclear, but not cytoplasmic RNA, suggesting that messenger RNA is responding specifically to the glucocorticoids. Recent studies by Feigelson and Feigelson indicate that the incorporation of glycine 2-Cl-4 into acid-soluble adenine and total RNA was stimulated to about the same extent after treatment with cortisone, several amino acids, and ammonium salts. This lack of specificity cautions against interpreting some of the available data too precisely in terms of a relationship between changes in RNA turnover and the effects of glucocorticoids on enzyme induction. Other observations equally pertinent to this problem suggest that glucocorticoids may be acting indirectly as inducers of specific enzymes by altering the concentrations of amino acids in liver and other tissues.(rlJs) Among the adaptive enzymes which respond to cortisol or various stressproducing conditions (starvation, high protein diet, alloxan diabetes),

Nucleic acid content in nutritional muscular dystrophy

The present study confirmed previous data obtained by others that DNA and RNA content of liver and skeletal muscle increase in vitamin E deficiency. New data were obtained for kidney cortex and adrenal where elevated nucleic acid levels were found in the vitamin E-deprived animals. Attempts to isolate highly polymerized DNA from skeletal muscle were in part successful, but necessary solubilization of the product for further purification was difficult. However, spectrophotometric analyses of these purified fractions confirmed the increased DNA content in the skeletal muscle of E-deprived animals. Preliminary results on particulate fractions of kidney cortex cells indicate that the increment in RNA was associated with particles that sediment at 10,300 g. It would appear that a rise in DNA has occurred which cannot be explained by a concentration effect, leucocyte infiltration, or the mitotic process. It is suggested that this phenomenon is a reflection of an attempt at muscle regeneration which other mechanisms prevent.