Decrease In Adenosine Triphosphate Research Articles

Effects of carboxy-PTIO on systemic hemodynamics, liver energetics, and concentration of liver metabolites during endotoxic shock in rabbits: a 31P and 1H magnetic resonance spectroscopic study.

To investigate the effects of 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (carboxy-PTIO), a nitric oxide scavenger, on the lipopolysaccharide-induced hypotension, hepatocellular dysfunction, and liver damage in endotoxic rabbits. Experimental, comparative study. Laboratory of a university hospital. Eighteen Japanese white rabbits (3.0 to 3.2 kg body weight) anesthetized with ketamine-xylazine were studied. We randomly divided the rabbits into three groups: saline controls (group 1, n = 5); animals receiving lipopolysaccharide (400 micrograms/kg) alone (group 2, n = 8); and animals receiving lipopolysaccharide plus carboxy-PTIO at a rate of 0.17 mg/kg/min for 3 hrs (group 3, n = 5). Blood gases and mean arterial pressure (MAP) were monitored. In vivo phosphorus-31 magnetic resonance spectra were continuously obtained every 30 mins. In addition, the livers were sampled and underwent fractionation at 7 hrs after lipopolysaccharide administration. The hydrophilic and hydrophobic extracts from the livers were analyzed by in vitro hydrogen-1 and phosphorus-31 magnetic resonance spectroscopy. After the administration of lipopolysaccharide, the first phase of decrease in MAP within 30 mins was followed by partial recovery within the next 30 mins. In group 2, MAP started to decrease progressively within 180 mins after lipopolysaccharide administration (second phase) and decreased by 33% from the baseline value to 49 +/- 9 mm Hg at 420 mins. In contrast, the infusion of carboxy-PTIO significantly attenuated the second decrease in MAP (68 +/- 10 mm Hg, at 420 mins). In group 2, a slow and progressive decrease in adenosine triphosphate (ATP) and increase in inorganic phosphate concentrations occurred from 120 mins after lipopolysaccharide administration, and continued throughout the observation period. These changes were accompanied by a progressive decrease in intracellular pH. On the other hand, in group 3, there were no significant changes in ATP and inorganic phosphate concentrations compared with the controls from 120 to 360 mins after lipopolysaccharide administration. Moreover, restorations of both arterial and hepatocellular acidosis were observed in group 3. The differences of the degree of liver damage--as determined by the total amount of phospholipid, free fatty acids concentration, and membrane fluidity--were not significant among the three groups. Three of eight rabbits in group 2 died within 7 hrs, but no animal in the other two groups died during the study. The results of this study indicate that the infusion of carboxy-PTIO: a) prevented the delayed hypotension associated with endotoxic shock in rabbits; b) returned the hepatocellular ATP concentrations nearly to the level of the controls and alleviated hepatocellular acidosis; c) normalized various hydrophilic metabolites, such as lactate and alanine in the liver; and d) did not exacerbate liver injury after the administration of lipopolysaccharide. These findings indicate that carboxy-PTIO, a nitric oxide scavenger, may have a positive vasopressor effect during hypodynamic septic shock without exacerbating liver injury.

Excessive liver oxidant stress causes mortality in response to burn injury combined with endotoxin and is prevented with antioxidants.

We studied the effect of the oral administration of a water-soluble antioxidant solution containing ascorbic acid, glutathione, and a precursor for glutathione synthesis, N-Acetyl-L-cysteine, on liver antioxidant activity, liver cell energetics, and mortality in rats in response to a 20% third-degree burn injury challenged 5 days later with an intraperitoneal injection of 30 mg/kg endotoxin. Rats with burns were fluid-resuscitated with subcutaneous Ringer's lactate solution according to the Parkland formula (4 cc/kg/%burn). Rats challenged with endotoxin 5 days after burn were given an additional 100 ml/kg of subcutaneous Ringer's lactate solution immediately after the injection of endotoxin. A group of rats with burns challenged with endotoxin 5 days after burn were given an oral antioxidant solution beginning after burn injury. Liver cell energetics were measured as tissue energy charge potential (ECP), adenosine triphosphate (ATP) content, and total adenine nucleotides. The levels of endogenous liver glutathione, catalase, vitamin C, and vitamin E were measured to monitor antioxidant status. We found that burn injury alone did not produce any mortality over the 6-day period despite a 35% decrease in liver energy charge potential resulting from a decrease in ATP, a 34% decrease in liver catalase activity, and a 20% decrease in liver vitamin C. It was interesting that glutathione increased and vitamin E remained unchanged. We found that endotoxin injury combined with burn injury produced a 61% mortality rate with a 63% decrease in liver energy charge potential, again resulting from a decrease in ATP, a 74% decrease in liver catalase activity, a 16% decrease in vitamin C, and a 29% decrease in vitamin E. Glutathione was significantly decreased compared with burn alone. We compared the liver antioxidant status of survivors with that of nonsurvivors who were killed when appearing moribund and found that glutathione was decreased by 51% and vitamin C by 73% in nonsurvivors over that in survivors, whereas catalase and vitamin E levels were comparable between the two groups. The oral administration of the antioxidants prevented mortality and the decrease in antioxidant activity and attenuated the decrease in energy charge potential. We conclude that a 20% burn produces a modest decrease in liver energy charge potential and antioxidant defenses without producing mortality. The addition of endotoxin further decreases liver antioxidant defenses, liver energy charge potential, and markedly increases mortality. Antioxidants, given post-burn, restored antioxidant defenses, attenuated the altered cell energetics, and prevented mortality, indicating oxidants to be the cause of mortality. This data also suggests that a critical value of decreases in antioxidant defenses and ATP exists, resulting in mortality.

A Radiobiological Probe for Simultaneous NMR Spectroscopy and192Ir Gamma Irradiation ofSaccharomyces cerevisiae

A novel nuclear magnetic resonance (NMR) spectroscopy probe was designed and constructed for the study of transient metabolic changes in cellular systems during exposure to ionizing radiation. The probe incorporated a bioreactor, a radiation source, and a radiofrequency detection circuit tunable between 100 and 300 MHz forin vivoNMR spectroscopy of23Na,13C, and31P at 11.7 Tesla. The bioreactor system allowed perfusion, oxygenation, and temperature control of cultured cells during irradiation and while performing simultaneous spectroscopic experiments. The concentric design of the bioreactor allowed for the insertion of a192Ir gamma ray source (Eγ= 370 keV) to allow irradiation of the bioreactor system during the acquisition of NMR spectra. Initial results of31P spectra obtained during simultaneous gamma irradiation ofSaccharomyces cerevisiaeat approximately 8 Gy/hr show rapid decreases in adenosine triphosphate (ATP) and polyphosphate at the onset of irradiation followed by a slow recovery of polyphosphate.

Locomotory, ventilatory and metabolic responses of the subterranean Stenasellus virei (Crustacea, Isopoda) to severe hypoxia and subsequent recovery

The locomotory and ventilatory activities and the intermediary and energy metabolism modifications of the hypogean aquatic isopod crustacean Stenasellus virei were investigated in severe hypoxia (Po 2 < 0.03 kPa) and subsequent recovery. The aims of this study were i) to determine why the subterranean species displayed a greater tolerance of hypoxia than numerous other epigean crustaceans, ii) to confirm previous results obtained with four hypogean and epigean crustaceans, iii) to compare the responses to severe hypoxia in hypogean amphipods and isopods, and iv) to better understand the ecological problems of the hypogean organisms survival in subterranean habitats. S. virei responded to experimental long-term, severe hypoxia with classical anaerobic metabolism mainly characterized by a decrease in adenosine triphosphate (ATP) and phosphagen, utilization of glycogen and glutamate, and accumulation of lactate and alanine. Lactate was also largely excreted by this organism, which is unusual for crustaceans in general. Compared to most other epigean crustaceans, the isopod S. virei showed high amounts of stored glycogen and arginine phosphate. These differences in glycogen and phosphagen stores, and the ability to reduce energetic expenditures linked to locomotion and ventilation, extended the survival of S. virei under experimental anaerobiosis. During recovery, the isopod S. virei showed a higher capacity for glyconeogenesis from lactate and a faster and total replenishment of ATP and arginine phosphate levels than epigean crustaceans. Data concerning responses to hypoxia and subsequent recovery in S. virei are similar to those previously obtained with two other hypogean amphipods, except that this isopod did not synthesize succinate in anaerobiosis.

The Effects of 3000-Mhz Microwave Irradiation on Electroencephalic Energy and Energy Metabolism in Mouse Brain

To investigate the mechanism of effects of microwave irradiation on the central nervous system, 12 male LACA mice were irradiated with 3000-MHz microwave 1 h daily for 7 days at incident power density of 5 mW/cm2. Significant inhibitory effects were observed on total electroencephalic energy and peak electroencephalic energy of left and right central concatenated electrodes (channels 3 and 4) as compared to the control (p < 0.05 and/? < 0.01, respectively). It was also discovered that the adenosine triphosphate (ATP) in the brain and the amounts of succinate dehydrogenase (SDH) in the hypothalamus and hippocampus were reduced significantly in the irradiation group as compared to the control (p < 0.05). The mechanism might be as follows: the decrease in SDH causes the decrease in ATP, and then a lower ATP possibly results in lower electroencephalic energy. It is thus suggested that effects of microwave irradiation on central nervous system are relevant to electroencephalic energy.

Cytoprotection by fructose and other ketohexoses during bile salt-induced apoptosis of hepatocytes.

Toxic bile salts cause hepatocyte necrosis at high concentrations and apoptosis at lower concentrations. Although fructose prevents bile salt-induced necrosis, the effect of fructose on bile salt-induced apoptosis is unclear. Our aim was to determine if fructose also protects against bile salt-induced apoptosis. Fructose inhibited glycochenodeoxycholate (GCDC)-induced apoptosis in a concentration-dependent manner with a maximum inhibition of 72% +/- 10% at 10 mmol/L. First, we determined if fructose inhibited apoptosis by decreasing adenosine triphosphate (ATP) and intracellular pH (pHi). Although fructose decreased ATP to <25% of basal values, oligomycin (an ATP synthase inhibitor) did not inhibit apoptosis despite decreasing ATP to similar values. Fructose (10 mmol/L) decreased intracellular pH (pHi) by 0.2 U. However, extracellular acidification (pH 6.8), which decreased hepatocyte pHi 0.35 U and is known to inhibit necrosis, actually potentiated apoptosis 1.6-fold. Fructose cytoprotection also could not be explained by induction of bcl-2 transcription or metal chelation. Because we could not attribute fructose cytoprotection to metabolic effects, alterations in the expression of bcl-2, or metal chelation, we next determined if the poorly metabolized ketohexoses, tagatose and sorbose, also inhibited apoptosis; unexpectedly, both ketohexoses inhibited apoptosis. Because bile salt-induced apoptosis and necrosis are inhibited by fructose, these data suggest that similar processes initiate bile salt-induced hepatocyte necrosis and apoptosis. In contrast, acidosis, which inhibits necrosis, potentiates apoptosis. Thus, ketohexose-sensitive pathways appear to initiate both bile salt-induced cell apoptosis and necrosis, whereas dissimilar, pH-sensitive, effector mechanisms execute these two different cell death processes.

Cytoprotection by fructose and other ketohexoses during bile salt-induced apoptosis of hepatocytes

Toxic bile salts cause hepatocyte necrosis at high concentrations and apoptosis at lower concentrations. Although fructose prevents bile salt- induced necrosis, the effect of fructose on bile salt-induced apoptosis is unclear. Our aim was to determine if fructose also protects against bile salt-induced apoptosis. Fructose inhibited glycochenodeoxycholate (GCDC)-induced apoptosis in a concentration-dependent manner with a maximum inhibition of 72% +/- 10% at 10 mmol/L. First, we determined if fructose inhibited apoptosis by decreasing adenosine triphosphate (ATP) and intracellular pH (pHi). Although fructose decreased ATP to <25% of basal values, oligomycin (an ATP synthase inhibitor) did not inhibit apoptosis despite decreasing ATP to similar values. Fructose (10 mmol/L) decreased intracellular pH (pHi) by 0.2 U. However, extracellular acidification (pH 6.8), which decreased hepatocyte pHi 0.35 U and is known to inhibit necrosis, actually potentiated apoptosis 1.6-fold. Fructose cytoprotection also could not be explained by induction of bcl-2 transcription or metal chelation. Because we could not attribute fructose cytoprotection to metabolic effects, alterations in the expression of bcl-2, or metal chelation, we next determined if the poorly metabolized ketohexoses, tagatose and sorbose, also inhibited apoptosis; unexpectedly, both ketohexoses inhibited apoptosis. Because bile salt-induced apoptosis and necrosis are inhibited by fructose, these data suggest that similar processes initiate bile salt-induced hepatocyte necrosis and apoptosis. In contrast, acidosis, which inhibits necrosis, potentiates apoptosis. Thus, ketohexose-sensitive pathways appear to initiate both bile salt-induced cell apoptosis and necrosis, whereas dissimilar, pH-sensitive, effector mechanisms execute these two different cell death processes.(Hepatology 1997 Jan;25(1):81-6)

31P magnetic resonance spectroscopy detection of response-predictive adenosine triphosphate decrease in irradiated radiation-induced fibrosarcoma-1 tumors.

In previous phosphorus-31 (31P) magnetic resonance (MR) spectroscopy studies of radiation-induced fibrosarcoma (RIF-1), tumor model single-dose x-ray irradiation was applied at subcurative doses. A more effective x-ray does was used in this study, allowing correlation of treatment efficacy with the early changes observed in the 31P MR spectra of RIF-1 tumors. Subcutaneous RIF-1 tumors of 60 mice were examined by 31P MR spectroscopy shortly before a single localized x-ray dose of 40 Gy and at eight times (2, 12, 24, 48, 72, 120, 168, and 216 hours) thereafter. Early increases in the relative concentration of inorganic phosphate and decreases in adenosine triphosphate (ATP), most notably at 2 and 12 hours (each P < 0.00001), were observed that lasted up to 48 hours after irradiation. Phosphomonoester and tumor pH showed decreases that reversed even earlier. Reduction of ATP measured at 48 hours after irradiation was, however, correlated with percent tumor shrinkage observed during the subsequent weeks (r = -0.59; P < 0.00001). Sustained loss of RIF-1 tumor ATP is predictive of treatment efficacy. Temporary depression of high-energy phosphate in favor of inorganic phosphate does not necessarily lead to cell death.

Reconsideration of the sequence of rigor mortis through postmortem changes in adenosine nucleotides and lactic acid in different rat muscles

We examined the changes in adenosine triphosphate (ATP), lactic acid, adenosine diphosphate (ADP) and adenosine monophosphate (AMP) in five different rat muscles after death. Rigor mortis has been thought to occur simultaneously in dead muscles and hence to start in small muscles sooner than in large muscles. In this study we found that the rate of decrease in ATP was significantly different in each muscle. The greatest drop in ATP was observed in the masseter muscle. These findings contradict the conventional theory of rigor mortis. Similarly, the rates of change in ADP and lactic acid, which are thought to be related to the consumption or production of ATP, were different in each muscle. However, the rate of change of AMP was the same in each muscle.

Alanine Protects Liver From Injury Caused by D–Galactosamine and Ccl4

The liver is the main organ involved in amino acid metabolism, and it utilizes glucogenic amino acids as substrates for glucose or adenosine triphosphate (ATP), but this process is impaired in clinical and experimental liver diseases. In this study, we administered high doses of amino acids in rats or cultured hepatocytes with experimental models of liver injury to examine whether such supplementation could attenuate liver damage. We found that the addition of alanine reduced enzyme leakage from primary cultured rat hepatocytes treated with D-galactosamine (D-gal), while other amino acids did not. A significant decrease of lactate dehydrogenase (LDH) leakage was observed when cells were cultured with >6 from mmol/L alanine. Alanine also reduced enzyme leakage from normal hepatocytes that were not treated with D-gal. In D-gal-treated rats, constant infusion of a high dose of alanine significantly reduced the plasma transaminase and total bilirubin levels when compared with infusion of an amino acid mixture. Bolus administration of alanine significantly prevented the elevation of plasma transaminase levels and histological liver damage in CCl4-treated rats, while fructose-1,6 bisphosphate (FDP) had little effect. Alanine might promote the restoration of damaged liver in hepatotoxicant-treated rats, because significant effect was found after the elevation in plasma transaminase levels. Alanine also prevented the decrease of cellular ATP caused by D-gal and appeared to promote ATP production in primary cultured rat hepatocytes. These results indicate that alanine reduces experimental liver damage by a direct effect on hepatocytes.

Alanine protects liver from injury caused by D-galactosamine and CCl4

The liver is the main organ involved in amino acid metabolism, and it utilizes glucogenic amino acids as substrates for glucose or adenosine triphosphate (ATP), but this process is impaired in clinical and experimental liver diseases. In this study, we administered high doses of amino acids in rats or cultured hepatocytes with experimental models of liver injury to examine whether such supplementation could attenuate liver damage. We found that the addition of alanine reduced enzyme leakage from primary cultured rat hepatocytes treated with D- galactosamine (D-gal), while other amino acids did not. A significant decrease of lactate dehydrogenase (LDH) leakage was observed when cells were cultured with >6 from mmol/L alanine. Alanine also reduced enzyme leakage from normal hepatocytes that were not treated withD-gal. In D-gal-treated rats, constant infusion of a high dose of alanine significantly reduced the plasma transaminase and total bilirubin levels when compared with infusion of an amino acid mixture. Bolus administration of alanine significantly prevented the elevation of plasma transaminase levels and histological liver damage in CCl4- treated rats, while fructose-1,6 bisphosphate (FDP) had little effect. Alanine might promote the restoration of damaged liver in hepatotoxicant-treated rats, because significant effect was found after the elevation in plasma transaminase levels. Alanine also prevented the decrease of cellular ATP caused by D-gal and appeared to promote ATP production in primary cultured rat hepatocytes. These results indicate that alanine reduces experimental liver damage by a direct effect on hepatocytes. (Hepatology 1996 Jul;24(1):185-91)

Protective Effects of Ranolazine on Ventricular Fibrillation Induced by Activation of the ATP-Dependent Potassium Channel in the Rabbit Heart.

BACKGROUND: The authors studied the antifibrillatory effects of the adenosine-triphosphate (ATP)-sparing metabolic modulator ranolazine in a rabbit isolated heart model in which ventricular fibrillation occurs under conditions of hypoxia/reoxygenation in the presence of the ATP-dependent potassium channel opener pinacidil. METHODS AND RESULTS: Ten minutes after ranolazine or vehicle administration, addition of pinacidil (1.25 µM) to the buffer was followed by a 12-minute hypoxic period and 40 minutes of reoxygenation. At a reduced concentration of ranolazine (10 µM), ventricular fibrillation occurred in 60% of the hearts, compared to 89% in the control group (P = NS). In contrast, only three of nine hearts (33%) treated with 20 µM ranolazine developed ventricular fibrillation (P <.05 vs vehicle). Hemodynamic parameters including coronary perfusion pressure, left ventricular developed pressure, and +/-dP/dt were not affected by the presence of ranolazine in the perfusion medium. Ranolazine did not prevent or modify the negative inotropic or coronary vasodilator actions of pinacidil, suggesting a mechanism of action independent of potassium channel antagonism. CONCLUSIONS: Ranolazine significantly reduced the incidence of ventricular fibrillation in the hypoxic/reoxygenated heart exposed to the ATP-dependent potassium channel opener, pinacidil. The reported ability of ranolazine to prevent the decrease in cellular ATP during periods of a reduced oxygen supply may account for its observed antifibrillatory action. By maintaining intracellular ATP, ranolazine may modulate or prevent further opening of the ATP-dependent potassium channel in response to hypoxia and/or pinacidil.

Toxicity of phenolic wastewater to luminescent bacteria photobacterium phosphoreum and activated sludges

Ash-heap water (AHW - phenolic wastewater of local oil-shale industry) was analyzed for its phenolic composition using HPLC and for its relative toxicity using MicrotoxTM and BiotoxTM tests where inhibition of natural luminescence of photobacteria is used as toxicity endpoint. Most abundant components in AHW were phenol (84 mg/L) and p-cresol (70 mg/L). The 5-min EC50 values for AHW (the concentration of AHW, %, which reduces the light output of bacteria by 50% after being in contact with bacteria for 5 minutes) for BiotoxTM and MicrotoxTM tests were 1.5% and 0.6%, respectively. Also, the toxicity of AHW towards two different activated sludges (acclimatized and not acclimatized to phenolic wastewater) was evaluated using decrease of adenosine triphosphate (ATP) content of the sludge as toxicity endpoint. AHW was relatively non-toxic to activated sludges, especially to the acclimatized sludge. The respective 60-min EC50 value for AHW (the concentration of AHW, %, which decreases the ATP level of activated sludge compared to the non-exposed control by 50% after being in contact with sludge for 60 minutes) was 20-30% for non acclimatized sludge and 50-60% for acclimatized sludge. Therefore, the biopurification of AHW using an adapted activated sludge process could be considered feasible.

Enhanced arsenite-induced hepatic morphological and biochemical changes in phenobarbital-pretreated rats.

Changes in liver morphology and biochemistry have been assessed 16 hr after a sc injection of sodium arsenite [As(III), 75 mumol/kg] to control and phenobarbital (PB)-pretreated (80 mg/kg, ip daily for 3 days) adult male Wistar rats. As(III) administration to PB-pretreated rats [PB + As(III)] caused hydropic degeneration, total loss of glycogen, necrosis in some centrilobular zones, and an increase in lipid vacuoles around the periportal area. Electron microscopy showed an increased number of vacuoles and autophagosomes containing organelle-like material. There was a 30% decrease in total hepatic cytochrome P-450 (CYP450). O-dealkylation of ethoxy- and pentoxyresorufin and N-demethylation of benzphetamine decreased to 42, 32, and 30% of control values, respectively. 5-Aminolevulinic acid dehydrase decreased 25% from controls, and metal chelatase activities decreased to 25% of the PB-treated group. Injection of As(III) alone resulted in a mild increase in lipid-containing vacuoles around the periportal zone, a moderate loss of glycogen in midzonal areas, and, by electron microscopy, a dilatation of the bile canaliculi and an increase of the number of myelin-like structures. CYP450 content and the O-dealkylation of ethoxy- and pentoxyresorufin and N-demethylation of benzphetamine all decreased between 30 and 50%. These results demonstrate the greater susceptibility of the liver to injury following PB with compounds not requiring metabolic activation. The metabolic basis of these changes are unclear but may result from an increased demand for metabolic energy due to PB induction and decreased adenosine triphosphate synthesis caused by arsenic.

Toxicity of phenolic wastewater to luminescent bacteria photobacterium phosphoreum and activated sludges

Ash-heap water (AHW - phenolic wastewater of local oil-shale industry) was analyzed for its phenolic composition using HPLC and for its relative toxicity using Microtoxࡊ and Biotoxࡊ tests where inhibition of natural luminescence of photobacteria is used as toxicity endpoint. Most abundant components in AHW were phenol (84 mg/L) and p-cresol (70 mg/L). The 5-mm EC5O values for AHW (the concentration of AHW, %, which reduces the light output of bacteria by 50% after being in contact with bacteria for 5 minutes) for Biotox™ and Microtox™ tests were 1.5% and 0.6%, respectively.Also, the toxicity of AHW towards two different activated sludges (acclimatized and not acclimatized to phenolic wastewater) was evaluated using decrease of adenosine triphosphate (ATP) content of the sludge as toxicity endpoint. AHW was relatively non-toxic to activated sludges, especially to the acclimatized sludge. The respective 60-mm EC5O value for AHW (the concentration of AHW, %, which decreases the ATP level of activated sludge compared to the non-exposed control by 50% after being in contact with sludge for 60 minutes) was 20–30% for non acclimatized sludge and 50–60% for acclimatized sludge. Therefore, the biopurification of AHW using an adapted activated sludge process could be considered feasible.

Alterations of Remnant Liver Carnitine Palmitoyltransferase I Activity and Serum Carnitine Concentration after Partial Hepatectomy in Rats

Many authors agree that alteration of the energy substrate from glucose to free fatty acid occurs during the early stage after partial hepatectomy. An accelerative effect of carnitine on the early phase of liver regeneration was suggested in several reports, but much controversy prevails. Using male Wistar rats weighing about 200 g as subjects, we undertook partial hepatectomy with resection of the median and left lateral lobes (67%). Another group of rats undergoing a sham operation was compared. Rats were killed at 6, 24, 48, or 72 hr after the operation. The rate of synthesis of DNA and content of DNA in remnant Liver were chosen as regenerative indicators. Serum carnitine, free fatty acid and its metabolites, remnant liver carnitine palmitoyltransferase I (CPT-I) activity, high-energy phosphate (HEP), including adenosine triphosphate (ATP), and crestine phosphate (CP) were measured. The results showed a marked decrease of HEP, ATP, and CP with suddenly increased free fatty acid and total ketone body in serum that occurred during the early regenerating phase after partial hepatectomy. Serum L-carnitine also increased markedly in this early stage. The mitochondrial CPT-I activity in the remnant liver decreased significantly 24 hr after partial hepatectomy. Our data show that regenerating liver utilizes free fatty acids as an immediate main substrate. Mitochondrial respiration with a CPT-I effect could be an important reaction in this utilization.

Effect of Methylprednisolone on Metabolism and Contractility in the Stunned Myocardium

The effect of glucocorticoid on the metabolism and contractility in the stunned myocardium was examined by phosphorus 31 nuclear magnetic resonance (31P-NMR) in Langendorff rabbit hearts by use of an artificial blood substitute, perfluorochemical emulsion Flusol-43. After normothermic global ischemia of fifteen minutes, postischemic reperfusion of sixty-five minutes was carried out. Methylprednisolone sodium succinate (MPSS) was administered either prior to global ischemia or during postischemic reperfusion. Adenosine triphosphate (ATP), creatine phosphate (CrP), inorganic phosphate (Pi), pH, left ventricular systolic developed pressure (LV DevP) and coronary flow were continuously measured. Thirty-six hearts were divided into three experimental groups consisting of 12 hearts each; CONT consisted of controls, Pre-MPSS perfusion with MPSS-containing solution (10(-4)M) from forty-five minutes prior to global ischemia, and Post-MPSS with the same MPSS solution immediately after postischemic reperfusion. Pre-MPSS showed a significant inhibition of the increase in Pi and of the decrease in ATP and pH during global ischemia, in comparison with the other groups, and a suppression of the overshoot of CrP observed immediately after postischemic reperfusion. LV DevP of Pre-MPSS showed a marked improvement during the postischemic reperfusion as compared with CONT. In Post-MPSS, Pi was significantly increased and ATP decreased during the postischemic reperfusion as compared with the other two groups. There were no differences in coronary flow during postischemic reperfusion among the three groups. In conclusion MPSS has a beneficial effect on metabolism and contractility of the stunned myocardium when it is administered prior to ischemia.

Nicotinamide methylation and hepatic energy reserve: a study by liver perfusion in vitro

Background/Aims: The synthesis of pyridine nucleotides from nicotinamide requires adenosine triphosphate. In man when exogenous nicotinamide is poorly utilized in this synthesis, the excess follows a dissipative metabolic pathway and is excreted in urine as N-methylnicotinamide. In human cirrhosis N-methylnicotinamide serum levels are higher than normal, in basal condition and after nicotinamide oral load. The aim of this study was to verify N-methylnicotinamide production in relation to hepatic content of adenosine triphosphate during in vitro perfusion of rat liver, in normal conditions and after adenosine triphosphate depletion by metabolic stress. Methods: “Stress” was obtained by pre-washing with saline for 15 min before the perfusion with nutritive medium. Results: The adenosine triphosphate decrease in the stressed liver was 38% after pre-washing with saline and 80% at the end of nutritive perfusion. In control liver the corresponding decreases were 1% after pre-washing with nutritive medium and 65% at the end of perfusion with the same medium. The total nicotinamide adenine dinucleotide decreases were 44% and 56% in the stressed liver, and 19% and 52% in the control liver. The output levels of N-methylnicotinamide at 90 min of rat liver nutritive perfusion were 31.50±4.72 nmol/g for normal liver and 66.40±13.17 for stressed liver ( p<0.001). Liver adenosine triphosphate was inversely related to N-methylnicotinamide production ( r=0.93; p<0.001). Conclusions: These data suggest that nicotinamide methylation may be enhanced when there is hepatic adenosine triphosphate decrease and energy failure induced by hypoxia or metabolic stress, similar to that obtained in vitro by saline washing before perfusion with nutritive medium. This study shows that the evaluation of N-methylnicotinamide production in man (before and after nicotinamide load) might be useful to explore the energy state of diseased liver.

Inhibition of Insulin Receptor Phosphorylation by PC-1 Is Not Mediated by the Hydrolysis of Adenosine Triphosphate or the Generation of Adenosine

Individuals with insulin resistance show increased levels of PC-1 expression in skeletal muscle and fibroblasts, and in transfected cell lines that overexpress PC-1 there is a reduction in the insulin-stimulated insulin receptor tyrosine phosphorylation. As PC-1 is a type II transmembrane protein with extracellular phosphodiesterase and pyrophosphatase activity, increased expression of PC-1 at the cell surface will decrease extracellular adenosine triphosphate levels and increase extracellular adenosine levels. Consequently it is possible that PC-1-mediated insulin resistance could be caused either by a decrease in adenosine triphosphate or an indirect increase in adenosine levels. We have tested this hypothesis and find that the PC-1-mediated inhibition of insulin-stimulated insulin receptor autophosphorylation is not altered by agents that alter the level or action of adenosine. Further, a mutated PC-1 with a single amino acid change that abolishes the phosphodiesterase and pyrophosphatase activities is still able to inhibit insulin-stimulated insulin receptor phosphorylation. The results of these experiments indicate that the phosphodiesterase activity of PC-1 is not involved in the inhibition of insulin receptor autophosphorylation.

Trimetazidine: In vitro influence on heart mitochondrial function

The mechanism of action of the antianginal trimetazidine (TMZ) remains largely unknown. In cultured rat ventricular myocytes in physiologic conditions, TMZ (5 × 10−4M) reduced the plateau potential level, the upstroke velocity, and the spontaneous action potential rate. When the cardiomyocytes were submitted to hypoxia (150 or 240 minutes) in a glucose-free medium, treatment with TMZ largely prevented the hypoxia-induced electromechanical alterations, i.e., the decrease in plateau amplitude, in resting membrane potential, in action potential duration, in rate, and in contractility. No hypoxiainduced arrhythmia was observed in the TMZ-treated cells. Moreover, the lactate dehydrogenase leakage was significantly reduced in the TMZ-treated cardiomyocytes (−58% and −36%, after 150 and 240 minutes of hypoxia, respectively). The drug was not efficient in reducing the hypoxiainduced decrease in adenosine triphosphate (ATP) content. The cellular ATP content was slightly lower in the TMZ-treated cells in normoxic conditions and in hypoxic conditions, but only in the glucose-free medium. To investigate further the relation between TMZ and energy metabolism, the respiration parameters were measured in heart mitochondria isolated from control and TMZ-treated rats (6 mg/kg/day, 7 days) with different substrates. This treatment resulted in a slight alteration of pyruvate oxidation, which was observed in the absence and in the presence of TMZ (10−4M) in the respiration medium. Conversely, a potent inhibition of palmitoylcamitine oxidation was measured when TMZ was added to the respiration medium. Neither pretreatment of the rats, nor addition of TMZ to the medium affected the oxidation of glutamate or citrate. In conclusion, pretreatment of ventricular myocytes with TMZ resulted in an increased cell resistance to hypoxic stress, as was evident from electromechanical functions and lactate dehydrogenase leakage. This cytoprotective action of TMZ could be related to an effect of the drug in the fatty acid metabolism. The mechanism of action of the antianginal trimetazidine (TMZ) remains largely unknown. In cultured rat ventricular myocytes in physiologic conditions, TMZ (5 × 10−4M) reduced the plateau potential level, the upstroke velocity, and the spontaneous action potential rate. When the cardiomyocytes were submitted to hypoxia (150 or 240 minutes) in a glucose-free medium, treatment with TMZ largely prevented the hypoxia-induced electromechanical alterations, i.e., the decrease in plateau amplitude, in resting membrane potential, in action potential duration, in rate, and in contractility. No hypoxiainduced arrhythmia was observed in the TMZ-treated cells. Moreover, the lactate dehydrogenase leakage was significantly reduced in the TMZ-treated cardiomyocytes (−58% and −36%, after 150 and 240 minutes of hypoxia, respectively). The drug was not efficient in reducing the hypoxiainduced decrease in adenosine triphosphate (ATP) content. The cellular ATP content was slightly lower in the TMZ-treated cells in normoxic conditions and in hypoxic conditions, but only in the glucose-free medium. To investigate further the relation between TMZ and energy metabolism, the respiration parameters were measured in heart mitochondria isolated from control and TMZ-treated rats (6 mg/kg/day, 7 days) with different substrates. This treatment resulted in a slight alteration of pyruvate oxidation, which was observed in the absence and in the presence of TMZ (10−4M) in the respiration medium. Conversely, a potent inhibition of palmitoylcamitine oxidation was measured when TMZ was added to the respiration medium. Neither pretreatment of the rats, nor addition of TMZ to the medium affected the oxidation of glutamate or citrate. In conclusion, pretreatment of ventricular myocytes with TMZ resulted in an increased cell resistance to hypoxic stress, as was evident from electromechanical functions and lactate dehydrogenase leakage. This cytoprotective action of TMZ could be related to an effect of the drug in the fatty acid metabolism.