The estimation of creatine and of diacetyl

Facile High-Performance Liquid Chromatography Mass Spectrometry Method for Analysis of Cyclocreatine and Phosphocyclocreatine in Complex Mixtures of Amino Acids

Creatine transporter deficiency (CTD) is caused by a defect in the X-linked creatine transporter SLC6A8 gene leading to severe neurologic and physiologic conditions. Cyclocreatine and phosphocyclocreatine supplementation is seen as a potential treatment, but the presence of these compounds within commercially available dietary supplements presents the risk of self-medication. High-performance liquid chromatography-mass spectrometry (HPLC-MS) is an excellent technique to assess composition of complex amino acid mixtures. Herein, we have developed a facile HPLC-MS method using a cyano column in hydrophilic interaction liquid chromatography (HILIC) mode with isocratic elution over 4 min to identify the main components of two commercially available dietary supplements. The relative standard deviation (RSD) for retention time and extracted ion integrated area are <0.3% and 4%, respectively, showing excellent reproducibility. Cyclocreatine and phosphocyclocreatine were not detectable within the dietary supplements, even at ppm levels, demonstrating the power and importance of the developed HPLC-MS method in analyzing complex mixtures.

612. Steam distillation of taints from cream: II. Investigations on commercial equipment with use of diacetyl and acetoin as reference substances

The extent of removal of the reference substances diacetyl and acetoin from water and cream in the Vacreator under varied conditions of operation has been investigated.

1. It was not affected by change in diameter or length of the uptake-pipe, or, with water, by changing the position of the equilibrium-valve to the top of the uptake-pipe or by introduction of the steam at the bottom of the pasteurizer bend instead of at the normal steam inlet.

2. It was affected only slightly by inclusion of baffles in the uptake-pipe, to provide a more intimate contact of steam and cream.

3. With diacetyl in water it was not affected by introduction of the major proportion of the steam via the infuser connexion, and with diacetyl in cream it was not affected until the proportion of steam introduced via the infuser was greater than 50% of the total amount of steam used. With acetoin in both water and cream there was a progressive slight reduction in extent of reference substance removal with increase in proportion of steam introduced via the infuser.

4. With diacetyl and acetoin in water it was not affected by increase in rate of flow of steam and cream at constant intensity of treatment.

5. With diacetyl it was not affected by temperature of steam distillation over the range 138–197°F., but with acetoin there was a progressive reduction in extent of removal with decrease in distillation temperature.

6. Steam is most effectively used if it is applied in separate stages instead of in one stage, i.e., a multiple Vacreator uses steam more efficiently than a single-unit machine. This effect is more marked with diacetyl, which has a high equilibrium coefficient, than with acetoin, which has a low coefficient.

7. The equilibrium coefficient computed from steam treatment of diacetyl solutions in the Vacreator is of the same order as that determined by the laboratory continuous equilibrium vaporization apparatus.

8. The efficiency of cream-deodorization equipment may be lowered by condensation of vapour back into the liquid, e.g. by use of excess cooling water in the Vacreator jackets.

9. There are indications that removal of diacetyl from cream is somewhat slower than from water.

The thanks of the author are due to Mr J. K. Scott for helpful discussion, to Mr E. R. Elley who did the analytical work, and to Mr B. Le Heron for assistance in the operation of the Vacreator and collection of samples.

596. Steam distillation of taints from cream: I. Theoretical considerations and properties of the reference substances, diacetyl and acetoin

The rate of removal of a dissolved tainting substance from cream by steam-distillation treatment is dependent in part on the relative volatility (or boiling point) of the pure substance, in part on the temperature of steam distillation, and in part on the influence of water on the vapour pressure of the tainting substance in dilute solution (i.e. on the activity coefficient, γ).

The application of Raoult's law and Henry's law to the problem of removal of taints from cream is discussed. For the dilute solutions commonly encountered in cream Henry's law can be expected to apply.

The equilibrium relationships for diacetyl and acetoin used as reference substances in investigations on cream-deodorizing equipment have been determined. The equilibrium coefficient for diacetyl in water at concentrations up to 50 p.p.m. in the liquid, as measured by the continuous equilibrium vaporization method, is 39·3. With rise in concentration above 50 p.p.m. in the liquid the coefficient decreases. At 100 p.p.m. it is 32 and at 1000 p.p.m. it is 20. The coefficient for acetoin in water at all concentrations up to 1·2% in the liquid is constant at 1·29. The activity coefficient for diacetyl in concentrations up to 50 p.p.m. was found to be 26·4 and for acetoin at concentrations up to 1·2%, 5·4.

For diacetyl the solubility partition coefficient as between butterfat and water rises from 0·47 at 100° F. to 0·74 at 180° F. For acetoin the partition coefficient remains constant at 0·18–0·19 over this range of temperatures. Correspondingly diacetyl is removed equally easily from butterfat and from water, whereas acetoin steam-distils much more readily from butterfat than from water.

729. Characteristics of a presumptive pediococcus occurring in New Zealand Cheddar cheese

1. Cultural and biochemical details are given of a homofermentative species of lactic acid-producing bacteria, repeatedly isolated from typical maturing New Zealand Cheddar cheese.

2. The Gram-positive cocci, occurring mainly in pairs and tetrads in acid media, are greatly stimulated in growth by the presence of yeast or tomato extracts. The organism converts glucose into inactive lactic acid and smaller amounts of acetic acid.

3. With the exceptions that the organism does not ferment trehalose and is less tolerant to low pH and high concentrations of Teepol, all its characteristics are similar to those for the genusPediococcus, in particular to the type speciesP. cerevisiaeBalcke.

Utilization of citrate by lactobacilli isolated from dairy products

Twenty-five strains of lactobacilli isolated from dairy products, includingLactobacillus casei, Lactobacillus plantarumandLactobacillus brevisspecies, were grown in semi-defined media and examined for their ability to ferment citrate and produce formate. Of 7 strains ofL. casei, all utilized citrate to varying extents, as did 9 of 10 strains ofL. plantarumand 3 of 8 strains ofL. brevis.L. caseiproduced 19–35% of the theoretical yield of formate from the citrate utilized,L. plantarum0–11% andL. brevis0–28%. Of 2 strains ofL. caseitested for their abilities to ferment citrate in the presence of 2% lactose, strain C 5 was unaffected by lactose whereas strain C 2 showed a 45% decrease in the citrate utilized. However, lactose used at 2% concentration greatly reduced formate production byL. caseiC 5, which produced 62% of the theoretical yield of formate from citrate after 35 days in the absence of lactose and only 8% in its presence. The yield of diacetyl produced byL. caseiC 5 from citrate plus lactose (both at 2% concentration) was 145 times that produced from citrate alone, and 800 times that from lactose alone.

589. A chemical investigation of the volatile flavour principle of Cheddar cheese

1. Steam distillates containing the flavouring substance(s) from Cheddar cheese were examined chemically. After the volatile fatty acids had been removed, the only substances identified in the flavour concentrates were ethanol, butyraldehyde, ethyl acetate and ethyl butyrate. None of these compounds appeared to be connected with the cheese flavour.

2. The essential flavour compound(s) could not be identified but some of its properties were elucidated.

3. The findings of other workers that the lower volatile fatty acids, diacetyl and acetyl methyl carbinol contribute to Cheddar-cheese flavour could not be confirmed. Flavour tests with numerous other compounds failed to show that they contributed to the typical flavour of Cheddar cheese.

The author gratefully acknowledges the helpful criticism and advice of Dr H. R. White-head throughout the investigation.

A method of detecting dissimilation of citrate by lactic acid bacteria usingStreptococcus lactisvar.diacetilactisNCDO 1007

In suitable media the relationship between the citrate content and the acetoin formed by the growth ofStreptococcus lactisvar.diacetilactisNCDO 1007 is linear. An assay method for citrate is described which is based on this relationship. It has been used to assay the residual citrate in cultures of lactic acid bacteria and, therefore, to assess the ability of these bacteria to dissimilate citrate. Some suitable media for the test are described.

Dependence of myosin-ATPase on structure bound creatine kinase in cardiac myofibrils from rainbow trout and freshwater turtle

The influence of myofibrillar creatine kinase on the myosin-ATPase activity was examined in cardiac ventricular myofibrils isolated from rainbow trout (Oncorhynchus mykiss) and freshwater turtle (Trachemys scripta). The ATPase rate was assessed by recording the rephosphorylation of ADP by the pyruvate kinase reaction alone or together with the amount of creatine formed, when myofibrillar bound creatine kinase was activated with phosphocreatine. The steady-state concentration of ADP in the solution was varied through the activity of pyruvate kinase added to the solution. For rainbow trout myofibrils at a high pyruvate kinase activity, creatine kinase competed for ADP but did not influence the total ATPase activity. When the ADP concentration was elevated within the physiological range by lowering the pyruvate kinase activity, creatine kinase competed efficiently and increased the ATPase activity twice or more for both trout and turtle. As examined for trout myofibrils, the ATPase activity was reduced about four times by inhibiting the activity of myofibril-bound creatine kinase with iodoacetamide and this reduction was only partially counteracted, when the creatine kinase activity was restored by adding creatine kinase to the solution. Hence, the results suggest that myofibril-bound creatine kinase is needed to fully activate the myosin-ATPase activity in hearts from ectothermic vertebrates despite their low energy turn-over relative to endothermic species.

Functional coupling between nucleoside diphosphate kinase of the outer mitochondrial compartment and oxidative phosphorylation

In rat liver mitochondria all nucleoside diphosphate kinase of the outer compartment is associated with the outer surface of the outer membrane (Lipskaya, T. Yu., and Plakida, K. N. (2003) Biochemistry (Moscow), 68, 1136-1144). In the present study, three systems operating as ADP donors for oxidative phosphorylation have been investigated. The outer membrane bound nucleoside diphosphate kinase was the first system tested. Two others employed yeast hexokinase and yeast nucleoside diphosphate kinase. The two enzymes exhibited the same activity but could not bind to mitochondrial membranes. In all three systems, muscle creatine phosphokinase was the external agent competing with the oxidative phosphorylation system for ADP. Determination of mitochondrial respiration rate in the presence of increasing quantities of creatine phosphokinase revealed that at large excess of creatine phosphokinase activity over other kinase activities (of the three systems tested) and oxidative phosphorylation the creatine phosphokinase reaction reached a quasi-equilibrium state. Under these conditions equilibrium concentrations of all creatine phosphokinase substrates were determined and K(eq)app of this reaction was calculated for the system with yeast hexokinase. In samples containing active mitochondrial nucleoside diphosphate kinase the concentrations of ATP, creatine, and phosphocreatine were determined and the quasi-equilibrium concentration of ADP was calculated using the K(eq)app value. At balance of quasi-equilibrium concentrations of ADP and ATP/ADP ratio the mitochondrial respiration rate in the system containing nucleoside diphosphate kinase was 21% of the respiration rate assayed in the absence of creatine phosphokinase; in the system containing yeast hexokinase this parameter was only 7% of the respiration rate assayed in the absence of creatine phosphokinase. Substitution of mitochondrial nucleoside diphosphate kinase with yeast nucleoside diphosphate kinase abolished this difference. It is concluded that oxidative phosphorylation is accompanied by appearance of functional coupling between mitochondrial nucleoside diphosphate kinase and the oxidative phosphorylation system. Possible mechanisms of this coupling are discussed.

Relating structure to mechanism in creatine kinase

Found in all vertebrates, creatine kinase catalyzes the reversible reaction of creatine and ATP forming phosphocreatine and ADP. Phosphocreatine may be viewed as a reservoir of "high-energy phosphate" which is able to supply ATP, the primary energy source in bioenergetics, on demand. Consequently, creatine kinase plays a significant role in energy homeostasis of cells with intermittently high energy requirements. The enzyme is of clinical importance and its levels are routinely used as an indicator of myocardial and skeletal muscle disorders and for the diagnosis of acute myocardial infarction. First identified in 1928, the enzyme has undergone intensive investigation for over 75 years. There are four major isozymes, two cytosolic and two mitochondrial, which form dimers and octamers, respectively. Depending on the pH, the enzyme operates by a random or an ordered bimolecular mechanism, with the equilibrium lying towards phosphocreatine production. Evidence suggests that conversion of creatine to phosphocreatine occurs via the in-line transfer of a phosphoryl group from ATP. A recent X-ray structure of creatine kinase bound to a transition state analog complex confirmed many of the predictions based on kinetic, spectroscopic, and mutagenesis studies. This review summarizes and correlates the more significant mechanistic and structural studies on creatine kinase.

The effect of creatine supplementation on glucose uptake in rat skeletal muscle

Glucose transport in muscle is a function of the muscle metabolic state, as evidenced by the increase in glucose transport which occurs with conditions of altered aerobic metabolism such as hypoxia or contractile activity. The energy state of the muscle can be determined by the muscle phosphocreatine concentration. Dietary supplementation of creatine has been shown to increase both phosphocreatine (PCr) and creatine (TCr) levels in muscle, although not in the same proportion, so that the PCr/TCr ratio falls suggesting an altered energy state in the cell. The purpose of this study was to determine the effect of increased creatine content on glucose uptake in muscle. PCr and TCr were determined in plantaris muscles from rats following five weeks of dietary supplementation of creatine monohydrate (300 mg/kg/day). (3)H-2-deoxyglucose uptake was measured in epitrochlearis muscles incubated in the presence or absence of a maximally stimulating dose of insulin. Despite a significant increase in creatine content in muscle, neither basal nor insulin-stimulated glucose uptake was altered in creatine supplemented rats. Since PCr levels were not increased with creatine supplementation, these results suggest that the actual concentration of PCr is a more important determinant of glucose uptake than the PCr/TCr ratio.

Intracellular energetic units in red muscle cells

The kinetics of regulation of mitochondrial respiration by endogenous and exogenous ADP in muscle cells in situ was studied in skinned cardiac and skeletal muscle fibres. Endogenous ADP production was initiated by addition of MgATP; under these conditions the respiration rate and ADP concentration in the medium were dependent on the calcium concentration, and 70-80% of maximal rate of respiration was achieved at ADP concentration below 20 microM in the medium. In contrast, when exogenous ADP was added, maximal respiration rate was observed only at millimolar concentrations. An exogenous ADP-consuming system consisting of pyruvate kinase (PK; 20-40 units/ml) and phosphoenolpyruvate (PEP; 5 mM), totally suppressed respiration activated by exogenous ADP, but the respiration maintained by endogenous ADP was not suppressed by more than 20-40%. Creatine (20 mM) further activated respiration in the presence of ATP and PK+PEP. Short treatment with trypsin (50-500 nM for 5 min) decreased the apparent K(m) for exogenous ADP from 300-350 microM to 50-60 microM, increased inhibition of respiration by PK+PEP system up to 70-80%, with no changes in MgATPase activity and maximal respiration rates. Electron-microscopic observations showed detachment of mitochondria and disordering of the regular structure of the sarcomere after trypsin treatment. Two-dimensional electrophoresis revealed a group of at least seven low-molecular-mass proteins in cardiac skinned fibres which were very sensitive to trypsin and not present in glycolytic fibres, which have low apparent K(m) for exogenous ADP. It is concluded that, in oxidative muscle cells, mitochondria are incorporated into functional complexes ('intracellular energetic units') with adjacent ADP-producing systems in myofibrils and in sarcoplasmic reticulum, probably due to specific interaction with cytoskeletal elements responsible for mitochondrial distribution in the cell. It is suggested that these complexes represent the basic pattern of organization of muscle-cell energy metabolism.

Functional complexes of mitochondria with Ca,MgATPases of myofibrils and sarcoplasmic reticulum in muscle cells

Regulation of mitochondrial respiration in situ in the muscle cells was studied by using fully permeabilized muscle fibers and cardiomyocytes. The results show that the kinetics of regulation of mitochondrial respiration in situ by exogenous ADP are very different from the kinetics of its regulation by endogenous ADP. In cardiac and m. soleus fibers apparent K(m) for exogenous ADP in regulation of respiration was equal to 300-400 microM. However, when ADP production was initiated by intracellular ATPase reactions, the ADP concentration in the medium leveled off at about 40 microM when about 70% of maximal rate of respiration was achieved. Respiration rate maintained by intracellular ATPases was suppressed about 20-30% during exogenous trapping of ADP with excess pyruvate kinase (PK, 20 IU/ml) and phosphoenolpyruvate (PEP, 5 mM). ADP flux via the external PK+PEP system was decreased by half by activation of mitochondrial oxidative phosphorylation. Creatine (20 mM) further activated the respiration in the presence of PK+PEP. It is concluded that in oxidative muscle cells mitochondria behave as if they were incorporated into functional complexes with adjacent ADP producing systems - with the MgATPases in myofibrils and Ca,MgATPases of sarcoplasmic reticulum.

Macrocompartmentation of total creatine in cardiomyocytes revisited

Distribution of total creatine (free creatine + phosphocreatine) between two subcellular macrocompartments--mitochondrial matrix space and cytoplasm--in heart and skeletal muscle cells was reinvestigated by using a permeabilized cell technique. Isolated cardiomyocytes were treated with saponin (50 microg/ml for 30 min or 600 microg/ml for 1 min) to open the outer cellular membrane and release the metabolites from cytoplasm (cytoplasmic fraction, CF). All mitochondrial population in permeabilized cells remained intact: the outer membrane was impermeable for exogenous cytochrome c, the acceptor control index of respiration exceeded 10, the mitochondrial creatine kinase reaction was fully coupled to the adenine nucleotide translocator. Metabolites were released from mitochondrial fraction (MF) by 2-5% Triton X100. Total cellular pool of free creatine + phosphocreatine (69.6 +/- 2.1 nmoles per mg of protein) was found exclusively in CF and was practically absent in MF. When fibers were prepared from perfused rat hearts, cellular distribution of creatine was not dependent on functional state of the heart and only slightly modified by ischemia. It is concluded that there is no stable pool of creatine or phosphocreatine in the mitochondrial matrix in the intact muscle cells, and the total creatine pool is localized in only one macrocompartment--cytoplasm.

Oxidative metabolism in Pediococcus pentosaceus. I. Role of oxygen and catalase

Dobrogosz, Walter J. (Pennsylvania State University, University Park) and Robert W. Stone. Oxidative metabolism in Pediococcus pentosaceus. I. Role of oxygen and catalase. J. Bacteriol. 84:716-723. 1962.-Studies were conducted on the physiological behavior of several strains of Pediococcus pentosaceus isolated from alfalfa silages. Although these organisms are regarded as homofermentative lactic acid bacteria which metabolize carbohydrates via the classic reactions of glycolysis, this investigation showed that they were capable of developing other physiologically important reactions related to carbohydrate metabolism. Growth on glycerol, for example, was shown to depend on the development of aerobic reactions, and was directly related to the catalase content of the various strains tested. These organisms were shown to be devoid of a cytochrome system, thus implicating an active flavoprotein system in oxidative reactions. A study of the end products of aerobic glycerol metabolism suggested that glycerol was oxidized to the pyruvate level, with subsequent reactions involving pyruvate leading to the accumulation of lactate, acetate, acetoin, and CO(2) in a molar ratio of approximately 1:1:1:3.

Skeletal muscle function, oxygenation and biochemistry in an endotoxemic model of SIRS

We have developed a reproducible low-dose endotoxin model which is useful for the investigation of early SIRS. The data confirm that organ function cannot be inferred from whole animal data (e.g. SVR vs. MVR). Thus, the study of SIRS at the organ and cellular level is essential. Decreased skeletal muscle oxygen consumption with 4 Hz exercise in early SIRS may be related to depletion of physiologic reserves, especially microcirculatory reserves, as suggested by decreased myoglobin saturation and decreased energy charge. Using this model, we will investigate whether organ dysfunction in SIRS is due to oxygen-limited cellular ATP production or impaired cellular metabolism.

Ionic calcium content of light dense human red cells separated by Percoll density gradients

In this paper we have compared the adequacy of two methods using Percoll density gradients to separate light and dense erythrocytes from fresh human blood. After measuring the distribution of some classical age-markers such as haemoglobin, potassium and creatine contents, it was found that preformed gradients generated more stringent conditions for age-related density separations. Employing such gradients the free Ca2+ content of above sub-populations was assessed with Fura-2, under conditions where the viscosity effect was abolished. In five experiments, the free Ca2+ content (mean value +/- 1 S.D.) was 8.4 +/- 2.82 nM and 31.2 +/- 13.0 nM for the 7-10% lightest and densest cells, respectively. These results are discussed in connection to red cell senescence.

Free energy and enthalpy of ATP hydrolysis in the sarcoplasm

A rigorous calculation of the free energy available in vivo from ATP hydrolysis requires the following information which is not all available, namely: (i) intra­cellular pH, (ii) activities of all the species of reactants and products in sarcoplasm, (iii) thermodynamic data for all the reactions involved, including values for ionic strength and temperature dependence, and (iv) the extent of deviation from equilibrium conditions, i. e. during contraction. We shall discuss each of these factors in turn and state the assumptions made that allow the approximate calculation of the free energy made available by the following net reaction in the sarcoplasm: ATP +H 2 O → ADP + Pi + H + . (1) Although it can only be an approximation this calculation is useful since it will take into account recent thermodynamic measurements in vitro .

Energy-rich phosphate compounds in bull semen: comparison of their metabolism with anaerobic heat production and impedance change frequency

1. The concentrations of nucleotides and other energy rich phosphate compounds in bull spermatozoa and bull semen were examined at different times during anaerobic incubation at 37 °C. The variations in the concentrations of these compounds were compared with sperm heat production and impedance change frequency during anaerobic incubation. 2. Immediately after collection there were 129 ± 14 p μ moles ATP , 120 ± 15.5 p μ moles ADP and 271 ± 22 p μ moles AMP + HR (in approximately equal quantities) per sperma­tozoon. (10 3 p μ moles x sperm density = μ moles/ml. semen.) The correlation between ATP and ADP concentration per spermatozoon and the percentage of live spermatozoa in the sample was 0.89, P < 0.05. 3. During the whole period of incubation, which lasted 120 to 430 min, the following changes in sperm nucleotide content took place; ( a ) ATP decreased; ( b ) ADP decreased; ( c ) labile-P decreased; ( d ) AMP + HR increased; ( e ) there was no inverse relationship between ATP and ADP . 4. During the first hour of incubation, when there was a sharp fall in heat production and impedance change frequency, there was no comparable decline in ATP , ADP , or labile-P. In one experiment there was a 55% increase in ATP during this period. 5. Contrary to recent reports, compounds which were not nucleotides but which contained highly labile phosphate groups were found in bull semen. Their concentration was about 250 p μ moles/spermatozoon, of which 50 p μ moles was creatine phosphate. The possibility that the rest was acetyl phosphate or 1, 3-diphosphoglycerate is discussed. 6. When the anaerobic heat production of bull semen fell to zero, which in these experiments we established was not due to exhaustion of fructose in the external medium but to the low pH, ≼5.5, of the seminal plasma, there were still significant amounts of nucleotides present in the spermatozoa.

Crucial role of intracellular effectors on glycogenolysis in the isolated rat heart: potential consequences on the myocardial tolerance to ischemia

The role played by glycogenolysis in the ischemic heart has been recently put into question because it is suspected that a slowing down of this process could be beneficial for the tolerance of the myocardium to ischemia. The role of the intracellular effectors that control the rate of glycogenolysis has therefore regained interest. We aimed to understand the role played by those intracellular effectors which are directly related to the energy balance of the heart. To this end, we review some of the previously published data on this subject and we present new data obtained from P-31 and C-13 NMR spectroscopic measurement on isolated rat heart. Two conditions of ischemia were studied: 15 min global no-flow and 25 min low-flow ischemia. The hearts were isolated either from control animals or from rats pre-treated with isoproterenol (5 mg.kg-1 b.w. i.p.) 1 h before the perfusion in order to C-13 label glycogen stores. Our main results are as follows: (1) the biochemically determined glycogenolysis rate during the early phase of ischemia (up to 10-15 min) was larger in no-flow ischemia than in low-flow conditions for both groups, (2) direct measurement of the glycogenolysis rate, as determined by C-13 NMR, after labelling of the glycogen pool in the hearts from isoproterenol-treated rats, confirms the estimations from the biochemical data, (3) glycogenolysis was slower in the hearts from pre-treated animals than in control hearts for both conditions of ischemia, (4) the total activity of glycogen phosphorylase (a + b) increased, by 50%, after 5 min no-flow ischemia, whereas it decreased by 42% after the same time of low-flow ischemia. However, the ratio phosphorylase a/a + b was not altered, whatever the conditions, (5) the concentration of inorganic phosphate (Pi) increased sharply during the first minutes of ischemia, to values above 8-10 mM, under all conditions studied. The rate of increase was larger during no-flow ischemia than during low-flow ischemia. The concentration of Pi was thereafter higher in controls than in the hearts from isoproterenol-treated animals. The calculated cytosolic concentration of free 5'AMP increased sharply at the onset on ischemia, reaching in a few minutes values above 30 microM in controls and significantly lower values around 15 microM, in the hearts from isoproterenol-treated rats. (6) The hearts from isoproterenol-treated rats displayed a reduced intracellular acidosis, when compared to controls, under both conditions of ischemia. We conclude that the intracellular effectors, mainly free AMP, play an essential role in the control of glycogenolysis via allosteric control of phosphorylase b activity. The alteration in the concentration of free Pi, the substrate of both forms of phosphorylase, can be considered as determinant in the control of the rate of glycogenolysis. The attenuation of ischemia-induced intracellular acidosis in the hearts from isoproterenol-treated rats could be a consequence of a reduced glycogenolytic rate and is likely to be related to a better resumption of the mechanical function on reperfusion.

An approach to the in vitro study of the UTP/UDPglucose/UDP moiety-conserved cycle

The kinetic behavior of a moiety-conserved ternary cycle is tested experimentally. This system contains the enzymes UDPglucose pyrophosphorylase, glycogen synthase and nucleoside diphosphokinase, converting respectively UTP into UDPglucose, then into UDP and back to UTP in a cyclic manner. The UDPGlc P2ase and NDPK steps are made irreversible by addition of inorganic pyrophosphatase and phosphocreatine kinase, respectively. In order to predict both the evolution and the steady-state values of the various substrates, a model is derived, which takes into account the actual enzyme rate expressions and parameter values, as determined under our experimental conditions. In that model, the UTP, UDPglucose and UDP are taken as the variables, whereas the total concentration of the substrate pool and the four enzyme maximal activities are chosen as the control parameters. Depending upon the various parameter values, monostability, reversible bistability and irreversible transitions may theoretically occur. However, it turns out that some of these values for which multistability might occur, are not accessible experimentally. Under conditions of monostability, the evolutions of the three substrates as experimentally measured are shown to be in good qualitative and quantitative agreement with the model predictions. The relaxation times between two consecutive steady states when a parameter is varied, are shown to be long-lasting processes (several hours). That such an experimental ternary substrate cycle actually exhibits a low sensitivity to any perturbation, addresses the issue to knowing if the same property is likely to occur in vivo, or, in other words, do large moiety-conserved cycles act as metabolic buffers?

Comparison of the effects of 2,3-butanedione monoxime on force production, myosin light chain phosphorylation and chemical energy usage in intact and permeabilized smooth and skeletal muscles

The primary goal of this study was to determine the utility of 2,3-butanedione monoxime as a tool for determining and separating the chemical energy usage associated with force production from that of force-independent, or 'activation' processes in smooth and skeletal muscles. We determined the effects of 2,3-butanedione monoxime on force production, myosin light chain phosphorylation and high energy phosphate usage in intact and permeabilized smooth (rabbit taenia coli) and skeletal (mouse extensor digitorum longus) muscles. In the intact taenia coli, 2,3-butanedione monoxime depressed the tonic phase of the tetanus, contractures evoked by high potassium (90 mM) and by carbachol (10(-5) M) and the small force response evoked by these agonists after treatment with D-600 (10(-5) M). In the electrically stimulated intact taenia coli 2,3-butanedione monoxime (0-20 mM) caused a proportional inhibition of tetanic force output, myosin light chain phosphorylation and high energy phosphate usage (ED50 approximately 7 mM for all these parameters). At 20 mM 2,3-butanedione monoxime, force and energy usage fell to near zero and the degree of myosin light chain phosphorylation decreased to resting values, indicating a shut-down of both force-dependent and force-independent energy usage at high concentrations of 2,3-butanedione monoxime. In permeabilized taenia coli, 2,3-butanedione monoxime had little or no depressant effects on force production, ATPase activity or calcium sensitivity. 2,3-butanedione monoxime had a very modest inhibitory effect on the in vitro motility of unregulated actin filaments interacting with thiophosphorylated myosin. In solution, 2,3-butanedione monoxime inhibited myosin light chain kinase, but not the phosphatase (SMP-IV). These results suggest that the major effect of 2,3-butanedione monoxime is not on the contractile proteins themselves, but rather on calcium delivery during excitation, thereby reducing the degree of activation of myosin light chain kinase and subsequent activation of myosin by light chain phosphorylation. Thus, 2,3-butanedione monoxime is not useful for the determination of the energetics of activation processes in smooth muscle because of its inhibition of both force-dependent and force-independent processes. In contrast, in the intact mouse extensor digitorum longus, 2,3-butanedione monoxime inhibits tetanic force production (ED50 approximately 2 mM) to a much greater extent than myosin light chain phosphorylation. When 2,3-butanedione monoxime was used to manipulate force production in muscles at L(o), it was found that approximately 60% of the total energy usage was force-independent and the remainder was force-dependent.(ABSTRACT TRUNCATED AT 400 WORDS)

Effect of standard-dose versus high-dose epinephrine on myocardial high-energy phosphates during ventricular fibrillation and closed-chest CPR

STUDY OBJECTIVE

To evaluate the effects of standard-dose versus high-dose epinephrine on myocardial high-energy phosphate metabolism during resuscitation from cardiac arrest.

DESIGN

Prospective, nonrandomized, controlled study using a swine model of cardiac arrest and resuscitation.

INTERVENTIONS

After anesthesia, intravascular pressure instrumentation, and ten minutes of ventricular fibrillation arrest, closed-chest CPR was begun. After three minutes of CPR, animals were allocated to receive either 0.02 mg/kg i.v. standard-dose epinephrine (eight) or 0.2 mg/kg i.v. high-dose epinephrine (nine). The animals underwent thoracotomy and rapid-freezing transmural myocardial core biopsy for high-energy phosphate analysis 3.5 minutes after epinephrine administration. High-energy phosphate values were blindly determined using high-pressure liquid chromatography.

RESULTS

Intravascular pressure (mm Hg) and high-energy phosphate (nmol/mg protein) results for standard-dose epinephrine versus high-dose epinephrine are, respectively, coronary perfusion pressure, 15.3 +/- 7.8 versus 23.7 +/- 5.5 (P = .0009); phosphocreatine, 0.4 +/- 0.8 versus 6.2 +/- 4.4 (P = .0003); adenosine triphosphate, 9.8 +/- 4.8 versus 12.7 +/- 5.7 (P = .30); adenosine diphosphate, 5.4 +/- 2.1 versus 6.1 +/- 1.3 (P = .41); and adenylate charge, 0.68 +/- 0.12 versus 0.72 +/- 0.12 (P = .87).

CONCLUSION

High-dose epinephrine does not deplete myocardial high-energy phosphate when given in this model of prolonged ventricular fibrillation. High-dose epinephrine increases coronary perfusion pressure compared with standard-dose epinephrine. High-dose epinephrine administration repletes phosphocreatine during closed-chest CPR, thereby increasing myocardial energy stores.

High-energy phosphate levels in the cerebral artery during chronic vasospasm after subarachnoid hemorrhage

High-energy phosphate levels were measured in the canine cerebral artery during chronic vasospasm. Subarachnoid hemorrhage and vasospasm were induced by percutaneous injections of autologous venous blood into the cisterna magna. Narrowing of the artery was confirmed by angiography 7 days later. Levels of adenosine phosphates (adenosine triphosphate (ATP), adenosine diphosphate (ADP), and adenosine monophosphate (AMP)), guanosine phosphates (guanosine triphosphate (GTP) and guanosine diphosphate (GDP)), and creatine phosphate (CrP) in the basilar artery were quantified using high-performance liquid chromatography. The total creatine (Crtotal) content was measured by a spectrophotometric method after acid hydrolysis of CrP. Levels of ATP, GTP, and CrP were markedly reduced in the spastic arteries, and ratios of ATP:ADP, GTP:GDP, and CrP:Crtotal were significantly decreased. The results indicate a serious disturbance in the energy metabolism that takes place in the cerebral artery during chronic vasospasm.

Adrenergic stimulation of rat hearts with severely reduced cytosolic adenine nucleotide pool and [ATP]/[ADP]ratio

The effect of severe reduction of cytosolic adenine nucleotide (AdN) pool and [ATP]/[ADP] ratio (by 2-deoxyglucose treatment) on functional and metabolic responses of isovolumic rat heart to increased energy demand induced by coronary flow (CF) rise and isoproterenol (Iso) addition has been investigated. AdN-depleted hearts had reduced phosphocreatine (PCr, by 80%), ATP (by 75%), [ATP]/[ADP] (24 times) and pressure-rate product (PRP, by 60%). An elevation of CF was followed by the increase in PRP in control and AdN-depleted hearts by 40-45% with unchanged metabolic parameters. At increased CF, Iso caused a further rise in PRP in both groups due to elevation of heart rate; however maximal levels of PRP in the AdN-depleted group still remained lower than that of control (by 40%). Only in control experiments was Iso addition accompanied by an increase in the difference between left-ventricular end- and minimal diastolic pressure, cytosolic [Pi] and [ADP], and some decrease in PCr and [ATP]/[ADP]. These data imply that severely reduced cytosolic [ATP]/[ADP] does not prevent acceleration of Ca2+ turnover by Iso in cardiomyocytes, it but restricts maximal force development affecting the myofibrils.

Cardiac contractile function, oxygen consumption rate and cytosolic phosphates during inhibition of electron flux by amytal--a 31P-NMR study

In order to investigate the potential role of cytosolic phosphates ([ATP], [ADP] and [Pi]) in the integration of mitochondrial respiration and mechanical function in the perfused heart, inhibition of the substrate end of the respiratory chain by amytal has been employed. A stepwise increase in amytal concentration (from 0.2 to 1.2 mM) resulted in the progressive abolition of the cardiac oxygen consumption, rate (VO2) in hearts oxidizing pyruvate (5 mM). The inhibition curve for VO2 was S-shaped, with K0.5 = 1.1 mM, and independent of the initial VO2 values varied by coronary flow and isoproterenol (Iso) addition. ADP-stimulated respiration of isolated mitochondria (malate + pyruvate) was twice as sensitive to amytal inhibition, whereas state 2 respiration (before ADP addition) had the same sensitivity as cardiac VO2. Decrease in VO2 was followed by a decline in phosphocreatine (PCr) content and augmentation of Pi at nearly constant ATP level and intracellular pH as assessed by the 31P-NMR method. These changes were associated with an elevation of cytosolic free [ADP] and a reduction of the [ATP]/[ADP] ratio and ATP affinity calculated from creatine kinase equilibrium. Concomitantly, pressure-rate product (PRP), maximal rates of contraction and relaxation fell down and the end diastolic pressure (EDP) rose at all initial loads. Amytal-inhibited hearts retained the capability to respond to Iso stimulation (0.1 microM, about 50% enhancement of PRP) even at 1 mM amytal, but their response to elevation of coronary flow was greatly diminished. Alterations in the PRP value induced by the inhibitor at a fixed coronary flow correlated negatively with cytosolic [ADP] and [Pi], and positively with [ATP]/[ADP] and A(ATP). In contrast, EDP correlated with all these parameters in the opposite manner. However, when PRP was varied by coronary flow in the absence of the inhibitor or at its fixed concentrations, such correlations were absent. These data imply that cytosolic phosphates can serve as a feedback between energy production and utilization when the control point(s) is (are) at the mitochondria. In contrast, other regulatory mechanisms should be involved when control is distributed among different steps located both in energy producing and utilizing systems.