Energetics of muscle.

Displacement Reactions of Phosphorus(V) Compounds and Their Pentacoordinate Intermediates

1. A possible mechanism for the action of the K(ATP) channel opener diazoxide on the improvement of energy metabolism of ischaemic/reperfused hearts was examined. 2. Isolated, perfused rat hearts were subjected to 40 min ischaemia followed by 60 min reperfusion. Diazoxide at concentrations of 3 to 30 microM was present in the perfusion buffer for the last 15 min of pre-ischaemia. 3. Treatment of the perfused heart with diazoxide enhanced the post-ischaemic recovery of rate-pressure product, attenuated the post-ischaemic rise in left ventricular end-diastolic pressure, and suppressed the release of creatine kinase and purine nucleosides and bases from the reperfused heart. Treatment of the heart with diazoxide also restored myocardial ATP and creatine phosphate and attenuated the decrease in mitochondrial oxygen consumption rate after reperfusion. This attenuation was maintained at the end of ischaemia as well as at the end of reperfusion. 4. In another set of experiments, myocardial skinned bundles were incubated for 30 min under hypoxic conditions in the presence and absence of diazoxide, and then the mitochondrial oxygen consumption rate was determined. Hypoxia induced a decrease in the mitochondrial oxygen consumption rate of the skinned bundles to approximately 40% of the pre-hypoxic value. In contrast, treatment of the bundles with 30 microM diazoxide preserved the normal mitochondrial oxygen consumption rate during hypoxia. This effect was abolished concentration-dependently by the combined treatment with either the K(ATP) channel blocker glibenclamide or 5-hydroxydecanoate. 5. These results suggest that diazoxide is capable of attenuating ischaemia/reperfusion injury of isolated perfused hearts due to preservation of mitochondrial function during ischaemia.

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Preservation of mitochondrial function by diazoxide during sustained ischaemia in the rat heart

Die Reaktionen von Phosphor(v)-Verbindungen, in deren Verlauf Ubergange zwischen tetra- und pentakoordinierten Spezies stattfinden, werden in einer kritischen Ubersicht unter besonderer Berucksichtigung der stereochemischen Aspekte des Reaktionsmechanismus diskutiert. Die Diskussion schliest die Bildung und den Zerfall der stabilen Oxyphosphorane, die Michaelis-Arbusov-, Perkov- und Wittig-Reaktionen, die wechselseitigen Umwandlungen von Phosphanen und deren Oxiden sowie nucleophile Substitutionen an Phosphonium-Ionen mit ein. Umsetzungen von Phosphorsaureestern und verwandten Verbindungen werden in den Vordergrund gestellt. Die gesamte chemische Argumentation entstammt der Betrachtung derjenigen Faktoren, welche die Stabilitat von Phosphoran-Derivaten sowie die Geschwindigkeiten ihrer Bildung, ihres Zerfalls und ihrer Umordnungsprozesse durch Deformation, Knupfen und Losen von Bindungen bestimmen. Die einheitliche Behandlung dieses weiten Gebietes wird durch Vorstellungen ermoglicht,die erst zum Teil in einer vorangehenden Publikation[2] eingefuhrt wurden. Es wird aufgezeigt. Das eine umfassende mechanistische Interpretation eine Weiterentwicklung der bisherigen Konzeptionen erfordert, und das einige der fruheren Vorstellungen revisionsbedurftig sind.

Austausch‐Reaktionen von Phosphor(v)‐Verbindungen und ihre pentakoordinierten Zwischenstufen

Publisher Summary Nonequilibrium thermodynamics or the thermodynamics of irreversible processes extends and complements the classical method by the explicit introduction of time. It enables one to formulate a description of real processes rather than idealizations that happen in well-defined equilibrium states; the correlations it provides are between kinetic parameters. The most tractable processes are those that occur when the system is in a steady state. However, under stationary conditions, the state parameters of the system give no information about the processes occurring; to study these processes, it is necessary to look at their effects on the surroundings and indeed this is the essence of the approach. The resulting analysis immediately determines the number and nature of the degrees of freedom involved. The thermodynamic considerations lead to criteria that may help to distinguish between models of oxidative phosphorylation. These criteria neither depend on the isolation of an intermediate nor is it necessary to observe a component of hydrogen ion flow used for phosphorylation. It is necessary to determine the electrochemical potential difference of hydrogen and possibly of potassium across the mitochondrial membrane; however, the remaining parameters are evaluated externally. It is possible in principle to envisage conditions in which the flow of hydrogen ion across the membrane may be maintained non-zero and constant for brief periods

Nonequilibrium Thermodynamics and Its Application to Bioenergetics

The primary energy sources for all the organisms living on the Earth are either sunlight or the energy liberated during chemical transformations (mainly, oxidation) of certain substances – food. Within the cell this energy is transformed, accumulated, and then utilized to ensure a multitude of processes (synthesis of new low- and high-molecular compounds, muscle contraction, luminescence, transfer of ions counter to their concentration gradients, etc.).The role of universal ‘energy keeper’, of the, as it were, ‘energy small change’ in biology is played by the molecules of adenosine tri- phosphate (ATP) whose hydrolytic dissociation in water solutions with the formation of adenosine diphosphate (ADP) and inorganic phosphate (P1) is accompanied by a rather strong decrease of system energy.†

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0033583500002286

Energetics of muscle.

Citations

Displacement Reactions of Phosphorus(V) Compounds and Their Pentacoordinate Intermediates

Preservation of mitochondrial function by diazoxide during sustained ischaemia in the rat heart

Austausch‐Reaktionen von Phosphor(v)‐Verbindungen und ihre pentakoordinierten Zwischenstufen

Nonequilibrium Thermodynamics and Its Application to Bioenergetics

The physical aspects of energy transduction in biological systems.

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