Effect of ethanol on the in vivo kinetics of thiamine phosphorylation and dephosphorylation in different organs of rat--II. Acute effects.

The effects of acute ethanol administration on different steps of thiamine (T), thiamine monophosphate (TMP) and pyrosphosphate (TPP) metabolism were determined in vivo in nervous tissues (cerebral cortex, cerebellum, brain stem and sciatic nerve) and in other tissues (small intestinal mucosa, kidney, heart, skeletal muscle and liver) of rats. The radioactivity of T and its phosphoesters in plasma and tissues was determined under steady-state conditions and at fixed time intervals (0.25-24 hr) after an i.p. injection of Thiazole-[2-14C]-thiamine (30 micrograms: 1.25 microCi) in the presence of a constant plasma ethanol concentration (37 mM; 1.75 g.l-1) produced by repeated intragastric administration of ethanol. Control animals received water intragastrically. Ethanol-treated rats and controls were starved, with water ad libitum during the 24 hr study period. Data were evaluated by using appropriate compartmental models, which allowed calculation of fractional rate constants, turnover rates and turnover times. In nervous tissues ethanol enhanced TMP entry (without affecting T entry or T and TMP release), reduced turnover time of total T and TPP, caused an almost general enhancement of TPP dephosphorylation without affecting T pyrophosphorylation, and increased markedly T content in the mixture released by tissues. Overall, ethanol appeared to enhance exchanges of T compounds in nervous tissues. In other tissues, the effects of ethanol were less consistent. Ethanol increased T uptake in kidney and liver and T release in liver and heart, but had no effect on T exchanges in the small intestinal mucosa and in skeletal muscle. In the presence of ethanol, TMP uptake increased in heart and skeletal muscle and decreased in the small intestinal mucosa, while TMP release decreased in heart and remained unchanged in all other organs. Turnover times tended to increase for total T and to decrease for TPP. T pyrophosphorylation was generally reduced, and T phosphates dephosphorylation generally enhanced. T became the most abundant component in the mixture released from all tissues.     

Effects of acute and chronic ethanol administration on thiamine metabolizing enzymes in some brain areas and in other organs of the rat

The effect of ethanol (4.7 g/kg body wt intragastrically as a single dose or once daily for 35 days) on the levels of the thiamine metabolizing enzymes (thiamine pyrophosphokinase, TPKase; thiamine pyrophosphatase, TPPase; and monophosphatase, TMPase) was studied in different organs (liver, kidney, small intestine, heart and skeletal muscle) and nervous regions (cerebral cortex, cerebellum, medulla oblongata, pons, corpus callosum, hypothalamus and sciatic nerve) of the rat. In order to evaluate the non-specific effects of the stress of gastric gavage and of the additional caloric intake, appropriate control groups of animals were treated intragastrically with water or with a saccharose solution isoenergetic with ethanol respectively. All animals were reared on a nutritionally adequate diet supplying amounts of thiamine higher than the recommended daily requirement. Enzymatic activities were determined quantitatively by biochemical methods. Tissue TPKase levels were generally reduced by both acute and chronic ethanol administration. TPPase levels were generally reduced after acute and increased after chronic ethanol treatment. Changes in brain TMPase levels were similar to those observed for TPPase. In visceral organs and skeletal muscle TMPase activity was increased by chronic ethanol treatment as compared to acute ethanol administration. In conclusion, ethanol exerts a marked influence on the tissue levels of the thiamine metabolizing enzymes: the activity of the enzymes dephosphorylating thiamine phosphates is increased whereas the activity of the thiamine pyrophosphate synthesizing enzyme is reduced. These changes may contribute to an important extent to the disturbances in thiamine cellular uptake and metabolism observed in alcoholism.     

Thiamine prevents obesity and obesity-associated metabolic disorders in OLETF rats

We previously found that thiamine mitigates metabolic disorders in spontaneously hypertensive rats, harboring defects in glucose and fatty acid metabolism. Mutation of thiamine transporter gene SLC19A2 is linked to type 2 diabetes mellitus. The current study extends our hypothesis that thiamine intervention may impact metabolic abnormalities in Otsuka Long-Evans Tokushima Fatty (OLETF) rats, exhibiting obesity and metabolic disorders similar to human metabolic syndrome. Male OLETF rats (4 wk old) were given free access to water containing either 0.2% or 0% of thiamine for 21 and 51 wk. At the end of treatment, blood parameters and cardiac functions were analyzed. After sacrifice, organs weights, histological findings, and hepatic pyruvate dehydrogenase (PDH) activity in the liver were evaluated. Thiamine intervention averted obesity and prevented metabolic disorders in OLETF rats which accompanied mitigation of reduced lipid oxidation and increased hepatic PDH activity. Histological evaluation revealed that thiamine alleviated adipocyte hypertrophy, steatosis in the liver, heart, and skeletal muscle, sinusoidal fibrosis with formation of basement membranes (called pseudocapillarization) which accompanied significantly reduced expression of laminin β1 and nidogen-1 mRNA, interstitial fibrosis in the heart and kidney, fatty degeneration in the pancreas, thickening of the basement membrane of the vasculature, and glomerulopathy and mononuclear cell infiltration in the kidney. Cardiac and renal functions were preserved in thiamine treatment. Thiamine has a potential to prevent obesity and metabolic disorders in OLETF rats.     

Cadmium turnover and changes of zinc and copper body status of rats continuously exposed to cadmium and ethanol

The effects of continuous exposure to cadmium (Cd) and ethanol on Cd turnover and zinc (Zn) and copper (Cu) body status of male Wistar rats were studied. The animals received an aqueous solution of 10% (w/v) ethanol and/or 50 mg Cd/l as the only drinking fluid for 12 weeks. The concentrations of Zn, Cu and Cd in the serum (or blood), liver, kidneys, spleen, brain, heart, femoral muscle and femur as well as in 24-h urine and faeces specimens were assessed by atomic absorption spectrometry (AAS). Ethanol alone had no effect on Cd accumulation or excretion. By contrast, co-administration of ethanol with Cd influenced the turnover of this toxic metal. Long-term consumption of ethanol alone caused a decrease in femur Zn and liver Cu concentrations. Moreover, the urinary loss of both bioelements decreased, whereas their faecal excretion was increased. Exposure to Cd resulted in an increase in liver and kidney and in a decrease in femur and 24-h urine Zn concentrations. An increase in Cu concentration in the kidney and a decrease in the brain were also noted. Moreover, Cd increased the total pool of Zn in organs (kidneys, liver, spleen, heart and brain), but did not influence that of Cu. Zn concentration in the liver, kidney and spleen of rats co-exposed to Cd and ethanol were increased, but were decreased in the brain and femur, compared to controls. The concentrations of Cu in livers and brains of these rats were decreased, whereas those in kidney, spleen and heart were increased. The urinary excretion of the elements was decreased, whereas their faecal excretion was increased. Moreover, the total amount of Cu in organs decreased below the control value and that of Zn was in the normal range. These changes in Zn and Cu levels could be explained by different effects of both toxic substances, differences in bioelement intakes (due to reduced consumption of drinking solutions and food), and the modifying effect of ethanol on Cd turnover. Our results suggest that alcoholics may be more susceptible to Cd accumulation and its effects on body Zn and Cu.     

Thiamine tetrahydrofurfuryl disulfide improves energy metabolism and physical performance during physical-fatigue loading in rats

Impaired energy metabolism is considered a possible cause of fatigue. The thiamine derivative, thiamine tetrahydrofurfuryl disulfide (TTFD), is prescribed and is also an over-the-counter drug for the attenuation of fatigue. It is readily absorbed from the intestinal tract and converted into thiamine pyrophosphate (TPP), which plays an important role as a cofactor for enzymes of metabolic pathways involved in the production of adenosine triphosphate (ATP). We postulated that TTFD has an anti-fatigue effect by improving energy metabolism during physical-fatigue loading. Here, we initially used the forced swimming test to determine whether daily TTFD or thiamine for 5 days has anti-fatigue effects on weight-loaded rats. The swimming duration of TTFD-, but not of thiamine-treated rats, was significantly longer than that of control rats (P < .05). Based on these findings, we examined changes in the levels of thiamine and its phosphate esters in various organs and the effect of TTFD on ATP levels in skeletal muscle after forced swimming, to determine the cellular mechanisms of the anti-fatigue effect of TTFD. Daily TTFD resulted in a characteristic distribution of thiamine and its phosphate esters in rat skeletal muscle, liver, kidney, heart, brain, and plasma. Furthermore, daily TTFD attenuated the decrease in ATP content in the skeletal muscle caused by forced swimming with a weight load for a defined period (150 s). These results indicate that TTFD exerts anti-fatigue effects by improving energy metabolism during physical fatigue.     

Changes in protein, RNA and DNA and rates of protein synthesis in muscle-containing tissues of the mature rat in response to ethanol feeding: a comparative study of heart, small intestine and gastrocnemius muscle.

1. The relative sensitivity of heart, small intestine and skeletal muscle to chronic ethanol feeding was investigated in mature Wistar rats fed ethanol as 36% of total energy intake; controls were fed the same diet in which ethanol was substituted by isoenergetic glucose. 2. Chronic ethanol feeding had no apparent effect on the protein, RNA and DNA contents of heart homogenates (atria and ventricles). The ratios of RNA/protein (synthetic capacity), RNA/DNA (synthetic material per nucleus) and protein/DNA (DNA-unit or apparent cell size) were also unaltered in the hearts of alcohol-fed rats. Fractional rates of cardiac protein synthesis (ks), and synthesis relative to RNA (kRNA) and DNA (kDNA) and absolute rates of protein synthesis (Vs) were unaffected by ethanol feeding. The total content of cardiac soluble proteins was unaltered by chronic ethanol feeding, but there were small and statistically significant decreases in the contents of the myofibrillar and stromal protein fractions. There were no differences in ks in any of the cardiac subcellular protein fractions. 3. In the small intestine, ethanol feeding had no statistically significant effect on either protein or RNA contents, but there was an apparent increase in RNA when expressed relative to either protein or DNA, though the DNA-unit was unaltered. There were also substantial decreases in ks, kRNA, kDNA and Vs of approximately 15-35%. 4. In the gastrocnemius, RNA contents were significantly reduced by ethanol feeding but protein and DNA contents were unaffected. Indices of the synthetic capacity and synthetic material per nucleus were also reduced, but the DNA-unit was unaltered. These observations were accompanied by approx. 15-30% reductions in ks, kRNA, kDNA and Vs in response to ethanol feeding. 5. It is concluded that various aspects of protein metabolism in the heart, small intestine and skeletal muscle are adversely affected by chronic ethanol toxicity. The characteristics and magnitude of the responses in each tissue differ. Effects in the heart may be subtle, though haemodynamic indices may ensue. The ethanol-induced alterations in the small intestine and skeletal muscle may be responsible for gastrointestinal disturbances in motility and skeletal muscle weakness, respectively.     

Glutathione turnover is increased during the acute phase of sepsis in rats

Glutathione metabolism during infection has been poorly documented. Glutathione concentrations and synthesis rates were studied in infected rats (2 d after infection) and in pair-fed controls. Glutathione synthesis rates were determined in liver, spleen, lung, small and large intestine, skeletal muscle, heart and blood by a 4-h or 6-h (15)N cysteine infusion. The activities of four hepatic enzymes involved in glutathione metabolism were also determined. Glutathione synthesis rates were significantly greater in liver (+465%), spleen (+388%), large intestine (+109%), lung (+100%), muscle (+91%) and heart (+80%) of infected rats compared with pair-fed controls. Glutathione concentrations were also greater in these tissues but were unaffected in small intestine and lower in blood. In keeping with the stimulation of liver glutathione synthesis, the activities of liver gamma-glutamyl-cysteine synthetase and glutathione reductase were significantly greater in liver of infected rats than of pair-fed rats. From the present study, we estimate that glutathione synthesis accounts for at least 40% of the enhanced cysteine utilization during infection. This increased utilization may be the primary cause of an enhanced cysteine requirement in infection.     

Changes in organ growth with feeding pattern. The influence of feeding frequency on the circadian rhythm of protein synthesis in the rat

The effect of eating one large meal rather than several small meals per day on protein metabolism and the growth of individual organs was investigated in young male rats. Meal-eating did not affect the rate of protein catabolism in liver, kidney, small intestine, or spleen in vivo compared with continously fed control animals that consumed the same total amount of food. A circadian rhythm of protein synthesis was found in liver and kidney slices taken from normal rats killed at various times; starvation reduced the magnitude of protein synthesis but did not alter its cyclical nature. Consumption of the daily food all in one meal distorted the circadian rhythm, particularly when it was taken in the morning, and a morning meal increased the total 24 hour synthesis of protein in liver whereas an evening meal did not. Meal-feeding in the morning increased the weights of the liver, small intestine and tibia compared with continuously fed rats, but meal-feeding in the evening did not.     

Protein metabolism in alcoholism: effects on specific tissues and the whole body.

Ethanol is one of the few nutrients that is profoundly toxic. Alcohol causes both whole-body and tissue-specific changes in protein metabolism. Chronic ethanol missuse increases nitrogen excretion with concomitant loss of lean tissue mass. Even acute doses of alcohol elicit increased nitrogen excretion. The loss of skeletal muscle protein (i.e., chronic alcoholic myopathy) is one of several adverse reactions to alcohol and occurs in up to two-thirds of all ethanol misusers. There are a variety of other diseases and tissue abnormalities that are entirely due to ethanol-induced changes in the amounts of individual proteins or groups of tissue proteins; for example, increased hepatic collagen in cirrhosis, reduction in myosin in cardiomyopathy, and loss of skeletal collagen in osteoporosis. Ethanol induces changes in protein metabolism in probably all organ or tissue systems. Clinical studies in alcoholic patients without overt liver disease show reduced rates of skeletal muscle protein synthesis though whole-body protein turnover does not appear to be significantly affected. Protein turnover studies in alcohol misusers are, however, subject to artifactual misinterpretations due to non-abstinence, dual substance misuse (e.g., cocaine or tobacco), specific nutritional deficiencies, or the presence of overt organ dysfunction. As a consequence, the most reliable data examining the effects of alcohol on protein metabolism is derived from animal studies, where nutritional elements of the dosing regimen can be strictly controlled. These studies indicate that, both chronically and acutely, alcohol causes reductions in skeletal muscle protein synthesis, as well as of skin, bone, and the small intestine. Chronically, animal studies also show increased urinary nitrogen excretion and loss of skeletal muscle protein. With respect to skeletal muscle, the reductions in protein synthesis do not appear to be due to the generation of reactive oxygen species, are not prevented with nitric oxide synthase inhibitors, and may be indirectly mediated by the reactive metabolite acetaldehyde. Changes in skeletal muscle protein metabolism have profound implications for whole body physiology, while protein turnover changes in organs such as the heart (exemplified by complex alterations in protein profiles) have important implications for cardiovascular function and morbidity.     

Ethanol effects on total sialic acid of various brain regions and visceral organs.

These experiments were designed to extend our earlier observations on acute ethanol effects on brain sialic acid (SA), an acidic sugar component of membrane gangliosides and many glycoproteins. Here, we tested for differential effects of ethanol on total sialic acid in various brain regions and for effects on other organs, such as liver, kidney, heart, and skeletal muscle. Subjects were young adult, male rats. The first experiment compared two commonly accepted analytical methods for brain SA on peripheral tissues. Consistently higher levels were evident with the resorcinol method in all tissues, especially in liver, compared with the thiobarbiturate method. Resorcinol-measured levels in the liver and kidney were on the order of 350 micrograms/g, wet weight. In the brain of controls, the resorcinol method revealed total SA levels to be on the order of 550-650 micrograms/g in the basal ganglia, cerebral cortex, cerebellum, and hippocampus. Brainstem levels were significantly lower. Ethanol, given IP at 2 g/kg, seemed to decrease total SA in all brain regions at four hours after injection, with statistically significant decreases in the hippocampus and brainstem. With 3 g/kg, only the cerebellum showed a significant decrease at four hours, compared to saline-injected controls, but the decrease was large (25%). Analysis of the other organs showed that, compared to saline-injected controls, ethanol decreased SA in the liver. There was a small, but significant, decrease in heart SA at four hours after 3 g/kg. In skeletal muscle, ethanol significantly increased total SA at 2 g/kg, but not at 3 g/kg.(ABSTRACT TRUNCATED AT 250 WORDS)     

Thiamine pyrophosphokinase activity in liver, heart and brain crude extracts of control and thiamine deficient rats.

The activity of thiamine pyrophosphokinase has been measured in liver, heart muscle and brain of normal and thiamine deficient rats. The activity measurement has been performed by use of thiamine-35S as substrate and separation of the reaction products by high voltage electrophoresis. KM has been determined as 7.1.10(-6) mol/l. The activity of thiamine pyrophosphokinase is reduced in liver and heart muscle of thiamine deficient rats significantly, whereas no decrease of the enzyme activity has been found in the brain. The content of thiamine pyrophosphate has been measured in the liver of normal and thiamine deficient rats. Injection of thiamine to deficient rats normalized the content of thiamine pyrophosphate in the liver within 6 hours. Our data suggest that thiamine pyrophosphokinase is an adaptive enzyme, the activity of which depends on the thiamine content of the cells.     

Are brain and heart tissue prone to the development of thiamine deficiency?

Thiamine deficiency is a continuing problem leading to beriberi and Wernicke's encephalopathy. The symptoms of thiamine deficiency develop in the heart, brain and neuronal tissue. Yet, it is unclear how rapid thiamine deficiency develops and which organs are prone to development of thiamine deficiency. We investigated these issues in a thiamine deficient animal model. Twenty-four male Lewis rats were fed a thiamine deficient diet, which contained 0.04% of normal thiamine intake. Six control rats were fed 200 μg of thiamine per day. Every week a group of six rats on the thiamine-deficient diet was sacrificed and blood, urine and tissue were stored. Blood and tissue transketolase activity, thiamine and thiamine metabolites were measured and PCR of thiamine transporter-1 (ThTr-1) was performed. Transketolase activity was significantly reduced in red blood cells, liver, lung, kidney and spleen tissue after two weeks of thiamine deficient diet. In brain tissue, transketolase activity was not reduced after up to four weeks of thiamine deficient diet. The amount of thiamine pyrophosphate was also significantly conserved in brain and heart tissue (decrease of 31% and 28% respectively), compared to other tissues (decrease of ∼70%) after four weeks of thiamine deficient diet. There was no difference between tissues in ThTr-1 expression after four weeks of thiamine deficient diet. Despite the fact that the heart and the brain are predilection sites for complications from thiamine deficiency, these tissues are protected against thiamine deficiency. Other organs could be suffering from thiamine deficiency without resulting in clinical signs of classic thiamine deficiency in beriberi and Wernicke's encephalopathy.     

Differential response of protein metabolism in splanchnic organs and muscle to pectin feeding

The aim of the present study was to determine whether the addition of soluble fibre in the diet affected protein metabolism in the intestinal tissues, some visceral organs and in skeletal muscle. A diet supplemented with pectin (80 g/kg) was fed to young growing rats and the effect on organ mass and protein metabolism in liver, spleen, small and large intestines and gastrocnemius muscle was monitored and compared with the control group. Protein synthesis rates were determined by measuring [13C]valine incorporation in tissue protein. In the pectin-fed rats compared with the controls, DM intake and body weight gain were reduced (9 and 20 %, respectively) as well as gastrocnemius muscle, liver and spleen weights (6, 14 and 11 %, respectively), but the intestinal tissues were increased (64 %). In the intestinal tissues all protein metabolism parameters (protein and RNA content, protein synthesis rate and translational efficiency) were increased in the pectin group. In liver the translational efficiency was also increased, whereas its protein and RNA contents were reduced in the pectin group. In gastrocnemius muscle, protein content, fractional and absolute protein synthesis rates and translational efficiency were lower in the pectin group. The stimulation of protein turnover in intestines and liver by soluble fibre such as pectins could be one of the factors that explain the decrease in muscle turnover and whole-body growth rate.     

二氧化硫吸入对小鼠9种脏器GSH和GSH/GSSG的影响

为研究二氧化硫 (SO2 )吸入后小鼠多种脏器内抗氧化物质谷胱甘肽 (GSH)和抗氧化系统GSH GSSG(GSSG为氧化型谷胱甘肽 )的变化 ,采用SO2 动态吸入染毒技术 ,使昆明小鼠吸入不同浓度SO2 后 ,用分光光度法测定不同脏器GSH含量 ,并计算GSH GSSG比值。结果表明 :(1)在SO2 浓度为 2 2mg m3时 ,雌、雄鼠所试脏器GSH水平和GSH GSSG均无显著变化 ;(2 )在SO2 浓度为 64mg m3时 ,雌鼠GSH水平和GSH GSSG变化不大 ,而雄鼠肺、肾、脑、胃、睾丸中GSH水平显著降低 ;(3 )在SO2 浓度为 148mg m3时 ,雌、雄鼠各脏器GSH水平和GSH GSSG均有下降 ,其中GSH在雄鼠肝、肺、肾、心、脑、胃、小肠、睾丸和雌鼠肝、肺、肾、小肠中下降显著 ,GSH GSSG在雄鼠肝、肾、小肠、睾丸和雌鼠肝、肺、肾、脑、胃、小肠中下降显著。以上结果说明一定浓度的SO2 吸入不仅影响小鼠呼吸器官 ,而且对多种脏器都有作用 ,同时显示雌、雄小鼠对SO2 的敏感性不同。GSH含量减少和GSH GSSG下降提示SO2 的毒作用与其降低体内抗氧化物质水平、削弱体内抗氧化防御系统有关     

二氧化硫对小鼠超氧化物歧化酶活性的影响

[目的]观察二氧化硫（SO2）对小鼠9种脏器超氧化物歧化酶（SOD）活性的影响。[方法]采用整体动物吸入染毒方式，测定小鼠吸入SO2气体后不同脏器SOD活性的变化。[结果]小鼠吸入较低浓度的SO2后，SOD活性变化因脏器而异；肝，肾，心，脾，脑，小肠，睾丸组织的SOD活性呈下降趋势，肺和胃组织的SOD活性呈上升趋势，但在较高SO2吸入浓度下，9种脏器SOD活性显著下降。[结论]SO2吸入体内会引起机体上述组织抗氧化能力下降。造成机体的氧化损伤。     

Effects of sustained ethanol intoxication and optimal nutrition on free amino acid levels in plasma,liver and muscle of the rat

The increased plasma levels of αamino-n-butyric acid (AANB) and branched chain amino acids (BCA) are commonly observed after chronic ethanol consumption. These changes are respectively attributed to enhanced turnover of hepatic glutathione (GSH) and increased muscle protein catabolism. On the other hand, the ethanol-induced decrease in plasma level of alanine (ALA) is thought to be caused by enhanced hepatic production of lactate. The objective of this study was to investigate how these alterations can be exhibited in rats subjected to sustained ethanol intoxication and concomitant optimal nutrition. Plasma lactate levels and content of free amino acids in the liver and gastroenemius muscle were also determined to facilitate better understanding of factors involved in the aforementioned changes. Male Wistar rats were intragastrically infused with liquid diet plus ethanol or isocaloric glucose for 30 days. This regimen resulted in sustained blood alcohol levels and optimal nutrition as indicated by similar weight gains of ethanol or pair-fed animals to that of chow-fed rats. Hepatic content and plasma concentrations of ALA were not decreased in the ethanol-fed group, and the plasma lactate levels in these animals were not different from those in the controls. Levels of BCA (valine, isoleucine, leucine) were increased by 42–44% in plasma and 15–23% in the muscle of the ethanol-fed rats. AANB concentrations were significantly increased by 5-fold in the muscle and by 4-fold in plasma with only a 2-fold increase in the liver. These data indicate that the reported ethanol-induced depression in the plasma level and liver content of ALA can be prevented by optimal nutrition. Furthermore, the increased plasma levels of AANB seem to be associated more closely with increased protein turnover in the muscle than with the enhanced GSH metabolism in the liver. The elevated BCA levels in plasma are also likely to be specific effects of ethanol stimulating the muscle protein turnover.     

Bioavailability and metabolism of (32P)malathion in the hen.

In this study separation of urine and faeces was made possible in the hen and bioavailability and metabolism of [³²P] malathion were studied after a single oral dose of 262.4 mg/kg. The results suggested that the compound is absorbed fairly rapidly from the gastrointestinal tract, significant quantities being detected in plasma and blood after 30 minutes of ingestion. Highest concentrations were present during the 6 to 8 hours following oral administration. At 6 hours, the concentration of ³²P was highest in liver followed by other organs. With the lapse of time the concentration in various organs decreased and at 48 hours, no ³²P was detected in heart, intestine, ovary, brain, adrenal, fat, muscle, and bone but traces (less than 5 μg/1 g) were present in liver, kidney, lung, and spleen. The cumulative urinary and faecal excretion study revealed that the compound was rapidly metabolised and 90% was excreted within 24 hours indicating thereby that the compound is rapidly excreted and accumulation in the system is unlikely.     

Effect of starvation in the rat on trimethyllysine in peptide linkage

Trimethyllysine residues in peptide linkage, precursors of carnitine biosynthesis, were measured in fed and 3-day fasted rats. Whole-body peptide-linked trimethyllysine in fasted rats was significantly less than in fed rats when expressed per initial body weight (17.8 vs 24.8 mumol/100 g initial body weight). Skeletal muscle had the highest peptide-linked trimethyllysine content (2.5 nmol/mg protein), followed by heart (1.9 nmol/mg protein). The content in kidney, liver and small intestine were similar, but less than in heart. Of the eight tissues tested, the brain had the only significant increase with fasting. The hepatic peptide-linked trimethyllysine in fasted rats was significantly decreased when expressed per milligram DNA. The study shows a commensurate loss of peptide-linked trimethyllysine accompanying protein loss during fasting. The study also shows that muscle contains over 65% of the whole-body peptide-linked trimethyllysine, and as such is a major reservoir of precursor for carnitine biosynthesis.     

Characterization of alpha-ketobutyrate metabolism in rat tissues: effects of dietary protein and fasting

The oxidative decarboxylation of alpha-ketobutyrate was studied in rat tissue preparations. Decarboxylation was confined to the mitochondrial fraction and required coenzyme A, NAD, TPP and FAD for optimal activity in solubilized preparations. The pH optimum for this reaction in liver was 7.8, somewhat higher than that reported for other alpha-keto acid dehydrogenases. An apparent Km of 0.63 mM for alpha-ketobutyrate was determined for the rat liver system. Competition by other alpha-keto acids at 10 mM concentrations inhibited enzyme activity up to 75%. Tissue distribution of alpha-ketobutyrate dehydrogenase activity relative to liver activity was (in percent): liver, 100; heart, 127; brain, 63; kidney, 57; skeletal muscle, 38; and small intestine, 7. Total liver alpha-ketobutyrate dehydrogenase was decreased by 40% after a 24-hour fast. Similar results were found for kidney and heart activity. alpha-Aminobutyrate-pyruvate aminotransferase activity in liver or kidney was not affected by fasting; however, it was induced in liver by 50% after feeding a 40% casein diet for 10 days compared to rats fed a 20% casein diet. Increasing the dietary casein content from 6 through 40% of the diet resulted in about a fivefold increase in liver alpha-ketobutyrate dehydrogenase activity. The substantial extrahepatic capacity for alpha-ketobutyrate metabolism makes it unlikely that a loss of liver function results in an inability to metabolize alpha-ketobutyrate. Whether alpha-ketobutyrate is decarboxylated by a specific enzyme or by an already characterized complex such as pyruvate dehydrogenase or the branched-chain keto acid dehydrogenase remains to be established.     

Biochemical and histological studies on thiamine-deficient and ethanol-fed rats.

Rats were separated into four groups and four different liquid diets were given to each group. Group 1: thiamine-sufficient diet with no ethanol, group 2: thiamine-sufficient diet with ethanol, group 3: thiamine-deficient diet with no ethanol, group 4: thiamine-deficient diet with ethanol. After four weeks, all rats were fasted for 24 hr and then ethanol was given orally to every rat. After one hour, every rat was sacrificed and biochemical and histological analyses were carried out. Transketolase activity in brain and liver decreased in groups 2, 3 and 4. There was significant decrease in transketolase activity in ethanol-fed groups (groups 2 and 4) as compared to control groups (groups 1 and 3). Ethanol concentrations in blood, liver and heart of rats in groups 2 and 4 were higher than in groups 1 and 3. When comparison was made between the thiamine-deficient groups and the corresponding thiamine-sufficient groups, ethanol concentrations in liver and heart were higher in the thiamine-deficient groups. Alcohol dehydrogenase activity in liver decreased significantly in groups 2 and 4. By histological analyses, fatty degeneration was observed in the livers of groups 2 and 4. The degeneration was more prominent in group 4 than group 2. These findings suggest that chronic ethanol administration may impair the ability to metabolize ethanol and the impairment may increase when rats are in the condition of thiamine deficiency.