I. V. Shemarova

Evolution of mechanisms of Ca2+-signaling: Role of calcium ions in signal transduction in prokaryotes

The review considers current concepts of mechanisms of Ca2+-signaling in cells of prokaryotes. Problems of structural-functional organization of the Ca2+-messenger system, mechanisms of membrane transport, and Ca2+ homeostasis are discussed. A special attention is paid to analysis of role of calcium ions and Ca2+-receptor proteins in regulation of intracellular processes in bacteria.

Evolution of Ca2+-Signaling Mechanisms. Role of Calcium Ions in Signal Transduction in Lower Eukaryotes

This review summarizes current concepts of Ca2+-signaling mechanisms in unicellular eukaryotes. Pathways of activation and transduction of Ca2+-signal are analyzed and the role of Ca2+ in regulation of cellular physiological processes is considered. A special attention is paid to evolutionary aspects of participation of Ca2+ ions and Ca2+-receptor proteins in regulation of intracellular processes.

Synthesis of New Derivatives of Pyrazolone and Nicotinic Acid and Study of Their Effect on Cytochrome P-450 Activity

At present, medicine employs preparations capable of inhibiting enzymes involved in the metabolism of xenobiotics; drugs of this type include, for example, iproniazid, imipramine, chlorcyclizine, and glutethimide [1, 2]. The purpose of this work was to synthesize Schiff bases from 4-aminopyrazolones, to synthesize hydrazones from nicotinic acid hydrazides and N-benzoyl-alanine, and to study the effect of the synthesized compounds on the activity of cytochrome P-450, which is the enzyme accelerating metabolism of many antiinflammatory preparations.

Action of La3+ on the systems providing contractility of vertebrate myocardium

The inotropic action of La3+ on frog myocardium was studied with taking into account its effect on mitochondria of cardiomyocytes (CM). It has been established that in the range of studied concentrations (0.2–6.0 mM), La3+ decreases dose-dependently the force of cardiac contractions (by 3.3–92.2%). In parallel experiments on isolated rat heart mitochondria (RHM), La3+ at a concentration of 25 μM has been shown to cause swelling of non-energized and energized mitochondria incubated in isotonic medium with 125 mM NH4NO3 and in hypotonic medium with 25 mM CH3COOK. The study of oxidative processes in mitochondria with aid of polarographic method of measurement of oxygen concentration has shown that La3+ at concentrations of 50 and 100 μM increases the oxygen consumption rate by mitochondria in the state 2. However, La3+ does not decrease the respiration rate of isolated mitochondria in the state 3, as this takes place in the case of use of Cd2+ or at the Ca2+-overloading of mitochondria. The rate of endogenous respiration of isolated mitochondria in the medium with La3+ was higher than in control, which suggests its effect on ion permeability of the inner membrane. The data obtained in this work indicate that the La3+-produced decrease of contractility of cardiac muscle is not only due to the direct blocking effect on the potential-controlled Ca2+-channels, but is also mediated by its unspecific action on the CM mitochondria. This action is manifested as an acceleration of the energy-dependent K+ transport in matrix and as an increase of ion permeability of the inner mitochondrial membrane (IMM).

Evolution of mechanisms of Ca2+-signaling. Significance of Ca2+-messenger systems during transition of organisms to multicellularity

The review considers Ca2+-messenger systems in primitive multicellulars (sponges and hydrozoa organisms). Analysis is performed of Ca2+ participation in regulation of early development of the organisms, their mobility, metamorphosis, chemoreception, and some other functions.

Comparative study of Y3+ effect on calcium-dependent processes in frog cardiac muscle and mitochondria of rat cardiomyocytes

Inotropic effects of yttrium acetate (Y3+) on contractions of myocardium preparations of the frog Rana ridibunda, as well as on respiration and the inner membrane potential (ΔΨmito) of isolated rat heart mitochondria were studied. 2 mM yttrium in Ringer solution was found to significantly reduce the amplitude of myocardium contractions, evoked by electric stimulation, and increase the half-relaxation time (n = 5). In experiments with Ca2+, Y3+ decreased the Ca2+-dependent basal respiration rate in rat heart mitochondria, energized by glutamate and malate, impeded the reduction in respiration of these mitochondria operating in state 3 after Chance or uncoupled by 2,4-dinitrophenol, and inhibited a Ca2+-induced reduction in their inner membrane potential. The data obtained are important for better understanding the mechanism underlying Y3+ effects on the myocardial Ca2+-dependent processes. Possible mechanisms of the negative inotropic effect of Y3+ on myocardium and its influence on the Ca2+-dependent processes in rat mitochondria are discussed.

Action of oxidative reactions in mitochondria on contractivity of heart muscle. Effects of Ni2

Inotropic effect of Ni2+ on mitochondrial oxidative reactions were studied on myocardium preparations excised from the left frog ventricle and the rat heart mitochondria (RHM), respectively. In the presence of 10–200 μM Ni2+, the cardiac contraction amplitude increased in the dose-dependent manner. It has been found that Ni2+ is not toxic for RHM. The state 4 by Chance in the KCl medium was stimulated by 100 μM Ni2+. At the same time, Ni2+ did not affect the state 3 and the 2,4-dinitrophenol-stimulated respiration of RHM. Our findings allow suggesting that the Ni2+-induced increase in the cardiac contraction amplitude is affected by energy state of the rat cardiomyocytic mitochondria.

Effect of Yttrium on Calcium-Dependent Processes in Vertebrate Myocardium

Inoptopic effect of yttrium acetate (Y3+) on myocardium of the marsh frog Rana ridibunda and its effect on ion transport across the inner mitochondrial membrane (IMM) of rat heart was studied. Y3+ was found to decrease the rate of heart contractions and to stimulate ion transport in the rat heart mitochondria in media with 10 mM glutamate and 2 mM malate. Presence of Y3+ induced inhibition of energy-dependent Ca2+ transport into mitochondria, which was expressed as a marked decrease of their swelling in the media containing 125 mM NH4NO3 and Ca2+ or 25 mM potassium acetate, 100 mM sucrose and Ca2+. It is suggested that the Y3+-induced decrease in rat muscle contractions is determined not only by direct suppressing effect of Y3+ on potential-modulated Ca2+-channels of pacemaker and contractile cardiomyocytes (CM), but also by its indirect effect on Ca2+-carrier in IMM. The data confirming that Y3+ activates energy-dependent K+ transport catalyzed by mitochondrial uniporter and blocks Ca2+-channels in the mitochondrial membrane are important for more complete understanding of mechanisms of the Y3+ action on vertebrates and human CM.

Effect of oxidative processes in mitochondria on contractility of heart muscle of the frog Rana temporaria. Actions of Cd2

The inotropic Cd2+ action on frog heart is studied with taking into account its toxic effects upon mitochondria. Cd2+ at concentrations of 1, 10, and 20 mM is established to decrease dose dependently (21.3, 50.3, and 72.0%, respectively) the muscle contraction amplitude; this is explained by its competitive action on the potential-controlled Na2+-channels of the L-type (Cav 1.2). In parallel experiments on isolated rat heart mitochondria (RHM) it was shown that Cd2+ at concentrations of 15 and 25 mM produces swelling of non-energized and energized mitochondria in isotonic (with KNO2 and NH2NO3) and hypoosmotic (with 25 mM CH3COOK) media. Study of oxidative processes in RHM by polarographic method has shown 20 mM Cd2+ to disturb activity of respiratory mitochondrial chain. The rate of endogenous respiration of isolated mitochondria in the medium with Cd2+ in the presence of malate and succinate was approximately 5 times lower than in control. In experimental preparations, addition into the medium of DNP—uncoupler of oxidation and phosphorylation did not cause an increase of the oxygen consumption rate. Thus, the obtained data indicate that a decrease in the cardiac muscle contractility caused by Cd2+ is due not only to its direct blocking action on Ca2+-channels, but also is mediated by toxic effect on rat heart mitochondria, which was manifested as an increase in ion permeability of the inner mitochondrial membrane (IMM), acceleration of the energy-dependent K+ transport into the matrix of mitochondria, and inhibition of their respiratory chain.

Peculiarities of Ca2+-regulation of functional activity of myocardium of frog Rana temporaria

To elucidate role of intra- and extracellular Ca2+ in regulation of rhythm and strength of frog heart contractions, there were studied ECC and isometric contraction of myocardium preparations in response to verapamil, adrenaline, and blockers of α- and β-adrenoreceptors. It has been shown that after an intramuscular injection of verapamil (6 mg/kg), bradycardia develops, the heart rate (HR) decreasing by 50–70%. Further, the cardiac arrest occurred; however, administration to the animals of adrenaline (100 mg/kg) restored the cardiac rhythm for a short while. After an intramuscular injection of adrenaline at doses of 0.1–10 mg/kg, no essential changes were observed in the potential action amplitude and HR; an increase of the administered adrenalin concentration to 100 mg/kg was not accompanied by the cardiac rhythm stimulation, as this takes place in homoiothermal animals and human; on the contrary, an essential HR deceleration was revealed. Phentolamine (5 mg/kg) gradually decelerated HR rhythm by 32–45%. The potential amplitude changed insignificantly. A subsequent intracardiac injection of adrenaline (100 mg/kg) on the background of block of α-adrenoreceptors produced acceleration of the rhythm (by 15–21%) and fall of the electrogram amplitude. These results can indicate that in the frog heart phentolamine interacts predominantly with α 1-adrenoreceptors. An intracardial administration of propranolol (1 mg/kg) to frogs promoted inhibition of β-adrenergic receptors and produced a gradual cardiac rhythm deceleration. In experiments on assessment of verapamil effect on the character of contractions this preparation at a concentration of 150 μM was established to produce a significant dose-dependent decrease of the contraction strength. A rise of verapamil concentration in the sample to 200 μM led to a decrease of the amplitude, on average, by 68–70% and in individual preparations—by 80–85%; however, administration into the sample of adrenaline (10 μM) restored the cardiac contraction strength. Adrenaline (1 nM–100 μM) increased markedly the contraction amplitude. Phentolamine (10 μM) did not inhibit transmission of contractile signal to cardiomyocytes; this was manifested in that the contraction amplitude after addition of adrenaline (10 μM) into the sample was approximately the same as in the sample containing no phentolamine. Propranolol (10 μM) eliminated the stimulatory action of adrenaline (10 μM). The results of these experiments indicate that in the frog ventricular cardiomyocytes the main adrenaline acceptors are β-adrenoreceptors.