Sepsis is associated with increased mRNAs of the ubiquitin-proteasome proteolytic pathway in human skeletal muscle.

Previous studies provided evidence that sepsis-induced muscle proteolysis in experimental animals is caused by increased ubiquitin-proteasome-dependent protein breakdown. It is not known if a similar mechanism accounts for muscle proteolysis in patients with sepsis. We determined mRNA levels for ubiquitin and the 20 S proteasome subunit HC3 by Northern blot analysis in muscle tissue from septic (n = 7) and non-septic (n = 11) patients. Plasma and muscle amino acid concentrations and concentrations in urine of 3-methylhistidine (3-MH), creatinine, and cortisol were measured at the time of surgery to assess the catabolic state of the patients. A three- to fourfold increase in mRNA levels for ubiquitin and HC3 was noted in muscle tissue from the septic patients concomitant with increased muscle levels of phenylalanine and 3-MH and reduced levels of glutamine. Total plasma amino acids were decreased by approximately 30% in the septic patients. The 3-MH/creatinine ratio in urine was almost doubled in septic patients. The cortisol levels in urine were higher in septic than in control patients but this difference did not reach statistical significance. The results suggest that sepsis is associated with increased mRNAs of the ubiquitin-proteasome pathway in human skeletal muscle.

Linkage of aerobic glycolysis to sodium-potassium transport in rat skeletal muscle. Implications for increased muscle lactate production in sepsis.

Although a linkage between aerobic glycolysis and sodium-potassium transport has been demonstrated in diaphragm, vascular smooth muscle, and other cells, it is not known whether this linkage occurs in skeletal muscle generally. Metabolism of intact hind-leg muscles from young rats was studied in vitro under aerobic incubation conditions. When sodium influx into rat extensor digitorum longus (EDL) and soleus muscles was facilitated by the sodium ionophore monensin, muscle weight gain and production of lactate and alanine were markedly stimulated in a dose-dependent manner. Although lactate production rose in both muscles, it was more pronounced in EDL than in soleus. Monensin-induced lactate production was inhibited by ouabain or by incubation in sodium-free medium. Preincubation in potassium-free medium followed by potassium re-addition also stimulated ouabain-inhibitable lactate release. Replacement of glucose in the incubation medium with pyruvate abolished monensin-induced lactate production but exacerbated monensin-induced weight gain. Muscles from septic or endotoxin-treated rats exhibited an increased rate of lactate production in vitro that was partially inhibited by ouabain. Increases muscle lactate production in sepsis may reflect linked increases in activity of the Na+, K+-ATPase, consumption of ATP and stimulation of aerobic glycolysis.

Energy-ubiquitin-dependent muscle proteolysis during sepsis in rats is regulated by glucocorticoids.

Recent studies suggest that sepsis-induced increase in muscle proteolysis mainly reflects energy-ubiquitin-dependent protein breakdown. We tested the hypothesis that glucocorticoids activate the energy-ubiquitin-dependent proteolytic pathway in skeletal muscle during sepsis. Rats underwent induction of sepsis by cecal ligation and puncture or were sham-operated and muscle protein breakdown rates were measured 16 h later. The glucocorticoid receptor antagonist RU 38486 or vehicle was administered to groups of septic and sham-operated rats. In other experiments, dexamethasone (2.5 or 10 mg/kg) was injected subcutaneously in normal rats. Total and myofibrillar proteolysis was determined in incubated extensor digitorum longus muscles as release of tyrosine and 3-methylhistidine, respectively. Energy-dependent proteolysis was determined in incubated muscles depleted of energy with 2-deoxyglucose and 2,4-dinitrophenol. Levels of muscle ubiquitin mRNA and free and conjugated ubiquitin were determined by Northern and Western blot, respectively. RU 38486 inhibited the sepsis-induced increase in total and myofibrillar energy-dependent protein breakdown rates and blunted the increase in ubiquitin mRNA levels and free ubiquitin. Some, but not all, sepsis-induced changes in ubiquitin protein conjugates were inhibited by RU 38486. Injection of dexamethasone in normal rats increased energy-dependent proteolysis and ubiquitin mRNA levels. The results suggest that glucocorticoids regulate the energy-ubiquitin-dependent proteolytic pathway in skeletal muscle during sepsis.

Sepsis stimulates nonlysosomal, energy-dependent proteolysis and increases ubiquitin mRNA levels in rat skeletal muscle.

We tested the role of different intracellular proteolytic pathways in sepsis-induced muscle proteolysis. Sepsis was induced in rats by cecal ligation and puncture; controls were sham operated. Total and myofibrillar proteolysis was determined in incubated extensor digitorum longus muscles as release of tyrosine and 3-methylhistidine, respectively. Lysosomal proteolysis was assessed by using the lysosomotropic agents NH4Cl, chloroquine, leupeptin, and methylamine. Ca(2+)-dependent proteolysis was determined in the absence or presence of Ca2+ or by blocking the Ca(2+)-dependent proteases calpain I and II. Energy-dependent proteolysis was determined in muscles depleted of ATP by 2-deoxyglucose and 2.4-dinitrophenol. Muscle ubiquitin mRNA and the concentrations of free and conjugated ubiquitin were determined by Northern and Western blots, respectively, to assess the role of the ATP-ubiquitin-dependent proteolytic pathway. Total and myofibrillar protein breakdown was increased during sepsis by 50 and 440%, respectively. Lysosomal and Ca(2+)-dependent proteolysis was similar in control and septic rats. In contrast, energy-dependent total and myofibrillar protein breakdown was increased by 172% and more than fourfold, respectively, in septic muscle. Ubiquitin mRNA was increased severalfold in septic muscle. The results suggest that the increase in muscle proteolysis during sepsis is due to an increase in nonlysosomal energy-dependent protein breakdown, which may involve the ubiquitin system.

Protein degradation in skeletal muscle during experimental hyperthyroidism in rats and the effect of beta-blocking agents.

beta-Blocking agents are increasingly used in the management of hyperthyroid patients. The effect of this treatment on increased muscle protein breakdown in the hyperthyroid state is not known. In the present study, experimental hyperthyroidism was induced in rats by daily ip injections of T3 (100 micrograms/100 g BW) during a 10-day period. Control animals received corresponding volumes of solvent. In groups of rats the selective beta-1-blocking agent metoprolol or the nonselective beta-blocker propranolol was infused by miniosmotic pumps implanted sc on the backs of the animals. Protein degradation was measured in incubated intact soleus and extensor digitorum longus muscles by determining tyrosine release into the incubation medium. The protein degradation rate in incubated extensor digitorum longus and soleus muscles was increased by 50-60% during T3 treatment. Metoprolol or propranolol did not influence muscle protein breakdown in either T3-treated or control animals. The results suggest that T3-induced increased muscle proteolysis is not mediated by beta-receptors, and muscle weakness and wasting in hyperthyroidism might not be affected by beta-blockers.

Insulin-like growth factor I reduces ubiquitin and ubiquitin-conjugating enzyme gene expression but does not inhibit muscle proteolysis in septic rats.

We examined the effect of insulin-like growth factor I (IGF-I), administered in vivo, on protein turnover rates and gene expression of the ubiquitin-proteasome proteolytic pathway in skeletal muscle of septic rats. Sepsis was induced by cecal ligation and puncture. Other rats were sham-operated. Miniosmotic pumps were implanted sc, and groups of rats received IGF-I (7 mg/kg x 24 h) or saline. Protein synthesis and breakdown rates were determined in incubated extensor digitorum longus muscles. Messenger RNA levels for ubiquitin and the ubiquitin-conjugating enzyme E2(14k) were determined by Northern blot analysis. Sepsis resulted in an approximately 30% reduction of muscle protein synthesis, and this effect of sepsis was blunted in rats treated with IGF-I. In contrast, IGF-I did not prevent the sepsis-induced increase in total and myofibrillar muscle protein breakdown. Ubiquitin and E2(14k) messenger RNA levels were increased several fold in muscle from septic rats, and this effect of sepsis was abolished in IGF-I treated rats. The results suggest that administration of IGF-I may improve sepsis-induced muscle cachexia by stimulating protein synthesis. However, because muscles were resistant to IGF-I, with regard to regulation of protein breakdown, the use of IGF-I to treat muscle cachexia during sepsis remains unclear. An additional important implication of the present study is that changes in messenger RNA levels for ubiquitin and the ubiquitin-conjugating enzyme E2(14k) do not always reflect changes in muscle protein breakdown rates.

Protein synthesis and quantitative morphology in thyroid tissue from hyperthyroid patients after preoperative treatment with antithyroid or beta-adrenergic antagonist drugs.

The rate of protein synthesis was measured in thyroid tissue obtained from three groups of patients undergoing thyroid surgery: group I (n = 18), hyperthyroid patients preoperatively treated with an antithyroid drug and T4; group II (n = 11), hyperthyroid patients preoperatively treated with a beta-adrenergic antagonist drug; and group III (n = 9), euthyroid patients operated on for multinodular goiter or adenoma. Quantitative morphology was studied in the resected thyroid tissue from the patients in groups I (n = 15) and II (n = 6) who had Graves' disease. While serum thyroid hormone levels became normal during preoperative treatment in group I, they remained elevated in the group II patients. The rate of protein synthesis was 2-fold higher in thyroid tissue from patients in group II than in those in groups I and III. A tendency toward an increased amount of epithelium and a reduced amount of colloid was found in thyroid tissue from patients in group II. There was a positive correlation between the rate of protein synthesis, and distribution of epithelium, and the epithelium to colloid ratio, respectively, in thyroid tissue. These results suggest that the thyroid gland of hyperthyroid patients remains hyperactive during treatment with beta-adrenergic antagonist drugs.

Protein metabolism in skeletal muscle tissue from hyperthyroid patients after preoperative treatment with antithyroid drug or selective beta-blocking agent. Results from a prospective, randomized study.

Protein metabolism in skeletal muscle tissue was studied in three groups of patients undergoing thyroid surgery: group I (n = 8), hyperthyroid patients preoperatively treated with an antithyroid drug and T4; group II (n = 8), hyperthyroid patients preoperatively treated with the beta 1-selective adrenoreceptor blocking agent metoprolol; group III (n = 5), euthyroid patients operated on for nodular goiter or adenoma. The study was prospective and hyperthyroid patients were randomly allocated to one of the two preoperative regimens. During operation a biopsy was taken from the sternohyoid muscle and rates of protein synthesis and degradation were measured in incubated muscle tissue. Clinical improvement was equal in the two groups of hyperthyroid patients during preoperative treatment but serum T3 concentrations remained elevated in patients treated with metoprolol. Thus, these patients were biochemically hyperthyroid at the time of operation. The rate of protein degradation was significantly higher in hyperthyroid patients treated with metoprolol than in patients of groups I and III. A significant positive correlation was found between serum T3 and rate of protein degradation in skeletal muscle. Protein synthesis rates were similar in the three groups of patients. This study demonstrated for the first time increased proteolysis in skeletal muscle tissue from patients with high serum T3 concentrations. The results indicate that changes of skeletal muscle protein metabolism in hyperthyroid patients are not normalized by beta 1-blockade despite the fact that this treatment effectively controlled symptoms and signs of hyperthyroidism.

Dexamethasone stimulates proteasome- and calcium-dependent proteolysis in cultured L6 myotubes.

The effect of dexamethasone on protein degradation and the involvement of different proteolytic pathways were examined in cultured L6 myotubes. Treatment of the cells with dexamethasone resulted in an approximately 20% increase in protein degradation at a hormone concentration of 10(-7) to 10(-6) M. By using various proteolytic blockers, evidence was found that the dexamethasone-induced increase in protein breakdown mainly reflected energy-proteasome-dependent proteolysis and to a lesser extent calcium-dependent protein breakdown. In contrast, the hormone treatment did not increase lysosomal proteolysis. mRNA levels for cathepsin B, ubiquitin, and the proteasome subunit C3 were increased by dexamethasone. The results suggest that glucocorticoids stimulate calcium and energy-proteasome-dependent muscle proteolysis and that changes in mRNA levels for proteolytic enzymes do not necessarily reflect the involvement of different proteolytic pathways.

Cytokines block the effects of insulin-like growth factor-I (IGF-I) on glucose uptake and lactate production in skeletal muscle but do not influence IGF-I-induced changes in protein turnover.

There is evidence that proinflammatory cytokines are involved in the regulation of muscle protein breakdown in various catabolic conditions but the mechanisms are not fully understood. Previous studies suggest that cytokines reduce circulating and tissue levels of insulin-like growth factor-I (IGF-I) and may block the anabolic effects of the hormone in certain cell types and tissues. We tested the hypothesis that a mixture of tumor necrosis factor alpha, interleukin-1 alpha, and interferon-gamma block the anabolic effects of IGF-I in skeletal muscle. Muscles from burned or unburned rats were incubated in the absence or presence of 1 microgram/mL of IGF-I with or without the addition of the cytokines. As expected, IGF-I stimulated protein synthesis and inhibited protein breakdown in incubated muscles. The cytokines did not influence protein turnover rates in muscles incubated with or without IGF-I. In additional experiments, the effects of IGF-I on glucose uptake and lactate production were tested. IGF-I increased glucose uptake approximately 2.5-fold and stimulated lactate production approximately 5-fold. These effects of the hormone were significantly inhibited by the cytokine mixture. The results suggest that cytokines do not induce protein catabolism by directly inhibiting the anabolic effects of IGF-I in muscle tissue. The inhibitory effects of the cytokines on IGF-I-stimulated glucose transport and lactate production suggest that the lack of effect of cytokines on protein metabolism was not due to a metabolic unresponsiveness of the incubated muscles to the cytokines.

Sepsis increases putrescine concentration and protein synthesis in mucosa of small intestine in rats.

Recent studies suggest that sepsis stimulates mucosal polyamine and protein synthesis. It is not known in which cell type polyamine biosynthesis is increased during sepsis and if polyamines regulate mucosal protein synthesis. We examined the effect of sepsis in rats on polyamine biosynthesis in isolated jejunal enterocytes and measured mucosal protein synthesis following inhibition of ornithine decarboxylase (ODC) activity with difluoromethylornithine. ODC and S-adenosylmethionine decarboxylase (SAMDC) activities and putrescine concentrations were increased in isolated jejunal enterocytes 16 h after induction of sepsis by cecal ligation and puncture. Enterocyte spermidine and spermine levels were not influenced by sepsis. Mucosal ODC and SAMDC activities and polyamine levels were increased following treatment of rats with interleukin-1 but not tumor necrosis factor. Treatment of rats with difluoromethylornithine prevented the sepsis-induced increase in mucosal ODC activity, putrescine concentration, and protein synthesis rate. The results suggest that sepsis increases ODC and SAMDC activities and putrescine concentrations in enterocytes of the small intestine. This metabolic response to sepsis may be regulated by interleukin-1 although other mechanisms may also be involved. Increased mucosal protein synthesis during sepsis may at least in part be regulated by increased putrescine levels.

Interleukin-1 beta and interferon-gamma regulate interleukin-6 production in cultured human intestinal epithelial cells.

Recent studies suggest that interleukin-6 (IL-6) is produced in the intestinal mucosa during sepsis and endotoxemia and that the enterocyte may be a source of IL-6 in these conditions. The regulation of IL-6 production in the enterocyte is not fully understood. We tested the hypothesis that IL-6 production in the enterocyte is regulated by proinflammatory cytokines. This was done by treating cultured Caco-2 cells, a transformed human intestinal epithelial cell line, with different concentrations of tumor necrosis factor-alpha (TNF-alpha), IL-1 beta, IL-6 or interferon-gamma (IFN-gamma). IL-6 production by the Caco-2 cells was determined by ELISA. The expression of IL-6 mRNA was determined by reverse-transcriptase polymerase chain reaction. IL-6 was not produced in unstimulated Caco-2 cells. Treatment of the Caco-2 cells with IL-1 beta resulted in a dose- and time-dependent stimulation of IL-6 production with a maximal effect noted at an IL-1 beta concentration of .5 ng/mL at 24 h. IFN-gamma alone did not stimulate IL-6 production but potentiated the effect of IL-1 beta in a synergistic fashion. Treatment of the Caco-2 cells with IL-1 beta induced expression of IL-6 mRNA with a response noticed after 30 min. TNF-alpha and IL-6 did not influence the production of IL-6 in the Caco-2 cells. The results suggest that enterocyte IL-6 production is stimulated by IL-1 beta and that this effect is potentiated by IFN-gamma. The regulation of IL-6 production in the enterocyte may be specific for IL-1 beta, since neither TNF nor IL-6 stimulated IL-6 production.

Sepsis stimulates polyamine biosynthesis in the liver and increases tissue levels of ornithine decarboxylase mRNA.

The influence of sepsis on polyamine metabolism in the liver was studied in rats. Sepsis was induced by cecal ligation and puncture; control rats were sham-operated. Sepsis resulted in increased concentrations in liver tissue of putrescine and spermidine and stimulated activity of the enzymes ornithine decarboxylase (ODC) and s-adenosylmethionine decarboxylase. A similar metabolic response was seen following the subcutaneous injection of 1 mg/kg of endotoxin or following the e intraperitoneal injection of 100 micrograms/kg of human recombinant tumor necrosis factor (TNF)-alpha or interleukin-1 alpha (IL-1 alpha). ODC mRNA levels determined by Northern blots were increased in liver tissue of septic rats, suggesting that the increase in ODC activity may be regulated at the transcriptional level although increased stability of the messenger could give rise to similar results. Treatment of rats with either TNF antiserum, recombinant IL-1 receptor antagonist, or the glucocorticoid receptor antagonist RU 38486, did not prevent the sepsis-induced increase in hepatic ODC activity. The data suggest that sepsis stimulates the biosynthesis of polyamines in liver tissue and that this response to sepsis may not primarily be mediated by TNF, IL-1, or glucocorticoids. The biological role of increased liver polyamines during sepsis, in particular their relationship with the synthesis of acute phase proteins, remains to be determined.

Interleukin-1beta induces complement component C3 and IL-6 production at the basolateral and apical membranes in a human intestinal epithelial cell line.

In previous studies, stimulation of cultured enterocytes with IL-1beta resulted in production of IL-6 and complement component C3. The cellular mechanisms of these responses in the enterocyte are not fully understood. We tested the hypothesis that IL-1beta-induced C3 and IL-6 production is differentially regulated at the apical and basolateral membranes of the enterocyte. Caco-2 cells (a transformed human colonic carcinoma cell line) were grown in a 2-chamber system to full differentiation. The cells were treated with IL-1beta either at the apical or basolateral membrane, and C3 and IL-6 mRNA levels and release of C3 and IL-6 into the apical and basal chambers were determined. The release of C3 was greatest into the basal chamber regardless of whether the cells were stimulated at the apical or basolateral membrane. In contrast, the production of IL-6 was greatest at the cell membrane that was stimulated with IL-1beta. Stimulation of the Caco-2 cells with IL-1beta resulted in increased mRNA levels for C3 and IL-6 with no major differences noted when the cells were treated at the apical or basolateral membrane. The results suggest that enterocyte production and release of at least some acute phase proteins and cytokines are differentially regulated at the apical and basolateral membrane of the enterocyte after stimulation with IL-1beta.

The transcription factor activator protein-1 is activated and interleukin-6 production is increased in interleukin-1beta-stimulated human enterocytes.

The intestinal mucosa is an active participant in the inflammatory and metabolic response to sepsis, endotoxemia, and other critical illness. The genes for various cytokines, e.g., interleukin 6 (IL-6), are regulated by multiple transcription factors, including nuclear factor-kappa B (NF-kappaB) and activator protein-1 (AP-1). In recent studies, treatment with IL-1beta of cultured Caco-2 cells, a human intestinal epithelial cell line, resulted in increased NF-kappaB DNA binding. The effect of IL-1beta on AP-1 activity in the enterocyte and the potential role of AP-1 in enterocyte IL-6 production are not known. We treated Caco-2 cells with IL-1beta and determined AP-1 activity by electrophoretic mobility shift assay (EMSA) and IL-6 production by enzyme-linked immunosorbent assay (ELISA). Treatment of Caco-2 cells with IL-1beta resulted in a dose- and time-dependent increase in AP-1 DNA binding. Supershift analysis suggests that activated AP-1 contained c-Jun, JunD, c-Fos, FosB, and Fra1 subunits. When Caco-2 cells were transiently transfected with an AP-1 luciferase reporter plasmid, stimulation with IL-1beta resulted in increased luciferase activity, suggesting that AP-1 DNA binding increased gene activation. Additional luciferase assays were performed with a plasmid containing a wild-type or AP-1-mutated IL-6 promoter. Stimulation of these cells with IL-1beta gave rise to results supporting the role of AP-1 in the regulation of IL-6 production. Geldanamycin, which has been shown in studies to inhibit AP-1 activation, blocked IL-1beta-induced AP-1 luciferase gene activation and IL-6 production. These results suggest that the AP-1 family of transcription factors is activated by IL-1beta in human enterocytes and that AP-1 may at least in part regulate IL-6 production in these cells.

Activation of NF-kappaB varies in different regions of the gastrointestinal tract during endotoxemia.

The transcription nuclear factor-kappaB (NF-kappaB) regulates a large number of genes involved in the inflammatory response to sepsis and endotoxemia. We recently found that NF-kappaB is activated in the jejunal mucosa during endotoxemia, but the response of NF-kappaB in other parts of the gastrointestinal tract is not known. We hypothesized that NF-kappaB is differentially activated in different regions of the gastrointestinal tract during endotoxemia. NF-kappaB DNA binding activity was determined by electrophoretic mobility shift assay in mucosa of the stomach, jejunum, ileum, and colon from endotoxemic and saline-injected mice. Cytoplasmic levels of the NF-kappaB inhibitory proteins IkappaB-alpha and IkappaB-beta were determined by Western blot analysis. Endotoxemia increased NF-kappaB activity in mucosa of stomach, jejunum, and ileum, with jejunum responding to smaller doses of endotoxin than the other parts of the gastrointestinal tract. NF-kappaB DNA binding activity was not induced in colonic mucosa, even following administration of high doses of endotoxin. IkappaB-alpha and IkappaB-beta levels decreased in jejunal mucosa of endotoxin injected mice, concomitant with activation of NF-kappaB. The results suggest that during endotoxemia, NF-kappaB is activated in mucosa of stomach and small intestine, but not in colon, and that the jejunum is particularly sensitive to endotoxin.

IL-1beta induction of NF-kappaB activation in human intestinal epithelial cells is independent of oxyradical signaling.

IL-1beta stimulation of cultured epithelial cells induces the degradation of IkappaBalpha and the consequent nuclear translocation of NF-lambdaB, a critical proinflammatory transcription factor in the mucosal host immune response. The role of reactive oxygen intermediates, serine protease activity, and tyrosine kinase activity in the activation of NF-kappaB is weakly conserved across various cell lineages and has not been defined in human enterocytes, a major target of oxidant stress in sepsis, thermal injury, and hemorrhagic shock. We report here that in Caco-2BBe cells, a transformed human colon cancer cell line with features of small intestinal epithelial cells in culture, exposure to oxidant stress (hydrogen peroxide 1-10 mM) did not induce NF-kappaB activation. Similarly, scavenging of free radicals and oxidants by pyrrolidine dithiocarbamate and dimethyl sulfoxide did not block IL-1beta-induced IkappaBalpha degradation and NF-kappaB activation. Genistein, a nonspecific tyrosine kinase inhibitor, also had no effect on IL-1beta-mediated effects on NF-kappaB. Serine protease inhibition by tosyl-lysine-chloromethylketone and tosyl-phenylalanine-chloromethylketone inhibited IkappaBalpha degradation and NF-kappaB activation stimulated by IL-1beta. Our data highlight the strong divergence between epithelial and mononuclear cells in the signal transduction pathways relating IL-1beta stimulation and NF-kappaB nuclear translocation.

Dantrolene reduces serum TNFalpha and corticosterone levels and muscle calcium, calpain gene expression, and protein breakdown in septic rats.

The effects of dantrolene on serum TNFalpha and corticosterone levels and on muscle calcium, calpain gene expression, and protein breakdown were studied in rats with abdominal sepsis induced by cecal ligation and puncture. Treatment of rats with 10 mg/kg of dantrolene 2 h before and 8 h after induction of sepsis reduced serum TNFalpha and corticosterone, muscle calcium levels, mRNA levels for m- and mu-calpain, and the muscle specific calpain p94, as well as total and myofibrillar protein breakdown rates, determined as release of tyrosine and 3-methylhistidine, respectively, from incubated extensor digitorum longus muscles. The results support the concept that increased calcium concentrations may be an important mechanism of sepsis-induced muscle protein breakdown. The data also indicate that other mechanisms, in addition to reduced muscle calcium concentrations such as decreased levels of TNFalpha and glucocorticoids, may contribute to the anti-catabolic effects of dantrolene during sepsis. The observations are important from a clinical standpoint because they suggest that the catabolic response in skeletal muscle during sepsis may be prevented by treatment with a calcium antagonist.

Septic encephalopathy. Etiology and management.

There are widespread disturbances in hepatic and peripheral metabolism in sepsis. Prominent effects include elevated plasma concentrations of aromatic and sulfur-containing amino acids during sepsis, while BCAA are normal or reduced. These alterations probably in part reflect accelerated muscle protein breakdown and hepatic dysfunction. Concomitant with changes in plasma amino acids, altered brain levels of amino acids and neurotransmitters are observed. Increased brain concentrations of the serotoninergic and reduced levels of the catecholaminergic neurotransmitters, along with the occurrence of false neurotransmitters, may be important factors in the pathophysiology of septic encephalopathy. Although the main objective in the treatment of septic patients, of course, is to remove or drain the septic focus, recent studies have shown that administration of BCAA-enriched solutions may be beneficial in the improvement of metabolic derangements and septic encephalopathy. It should be emphasized that not a great deal of work has been done in this area, and the above results are preliminary and fragmentary. However, they do at least provide a working hypothesis for testing of another form of metabolic encephalopathy.

Beneficial effect of allopurinol in liver ischemia.

The effect of allopurinol on protein synthesis, tissue water, and adenine nucleotides in liver tissue during and after a period of liver ischemia was investigated in rats. Ischemia was induced in the left and median liver lobes for 1 hour and experiments were continued for 2 hours after reperfusion. One group of animals (n = 20) received allopurinol (50 mg/kg body weight) intravenously 10 minutes before induction of liver ischemia. Control rats (n = 20) were given a corresponding volume of saline solution. Protein synthesis was measured by determining the rate of amino acid incorporation into protein in incubated liver slices. The reduction of protein synthesis and energy level in liver tissue and the increase of hepatic tissue water were similar in both groups of animals at the end of the ischemic period. During reperfusion the protein synthesis rate was higher and hepatic tissue water was lower in allopurinol-treated animals than in control rats. No significant differences in hepatic adenine nucleotides were found between the two groups of rats during ischemia or after reperfusion. The results demonstrated that improved protein synthesis and reduced tissue water in the postischemic liver after administration of allopurinol were not the result of improved restoration of adenine nucleotides. Inhibited production of oxygen-free radicals might be one mechanism by which allopurinol exerted its beneficial effect after liver ischemia.