[The electrophysiological characteristics of the plasma membrane of rat macrophages at rest and under exposure to ATP]. / Elektrofiziologicheskie kharakteristiki plazmaticheskoi membrany makrofagov krysy v pokoe i na fone vozdeistviia ATF.

The application of ATP in micromolar concentrations to the macrophages results in a biphasic response in the form of the short-time depolarization followed by a rather long hyperpolarization, the corresponding inward and outward macroscopic currents being observed. The ATP-induced hyperpolarization is accompanied by changes in current kinetics, I/V-curves pattern and shifting in the reversal potential. Such changes may be explained by a supposition that ATP activates an additional fraction of potassium channels with characteristics other than those in cells with initially low value of membrane potential. The data available are suggestive that in resting cells the inward rectification potassium conductance may dominate, whereas during ATP-induced hyperpolarization a certain type of Ca(2+)-dependent potassium conductance prevails. A rather high membrane potential in some part of macrophages, not treated with ATP, may be attributed to the latter type of conductance.

[Changes in the membrane potential of rat peritoneal macrophages under the extracellular action of ATP]. / Izmeneniia membrannogo potentsiala peritoneal'nykh makrofagov krysy pri ékstrkletochnom deistvii ATF.

In rat peritoneal macrophages the patch-clamp technique in whole-cell configuration was used to study modifications of membrane potential as a result of extracellular application of micromolar ATP concentration. The registered changes in membrane potential appeared to be of different form and polarization depending on the presence of Ca2+ in extracellular solution and on the concentration of calcium buffer inside the cell. A mechanism of membrane potential changes and their possible connection with the generation of a Ca2+ signal in the cell are discussed.

The action of blood serum and its components on potential-dependent sodium channels in neuroblastoma cells.

Blood plasma, serum and its fractions containing components of different molecular weights as well as some identified serum constituents were tested for their action on sodium currents of voltage-clamped, internally dialyzed neuroblastoma cells. Only components with a molecular weight over 50 kDa produced a persistent increase in sodium channel currents (stimulatory effect) and shifts in activation and inactivation curves along the voltage axis towards more negative or positive potentials, respectively (modifying effect). Both modulations taken together provide a somewhat higher level of sodium electro-excitable system activity. Among the identified serum components tested, including those possessing high physiological activity, albumin was the only one which reproduced the effects of whole blood serum both qualitatively and quantitatively. The data obtained allow to assume albumin to play a role of an active substance responsible for the blood plasma or serum effects on the potential-dependent transporting system in the neuroblastoma cell membrane. Albumin seems to be involved in holding the functional activity of sodium channels on a suitable level rather than being involved in any regulatory processes.

[Factors determining the functional activity of Na,K-ATPase]. / Faktory, opredeliaiushchie funktsional'nuiu aktivnost' Na,K-ATFazy.

A comparative estimation was made of modifications of Na,K-ATPase and Mg-ATPase parameters in the process of phylogenesis and as a result of sudden thermal selection. On the basis of our own and literary data a suggestion was put forward about the availability of quite different ways of thermal adaptation in ATP-hydrolyzing enzymes associated with different physiological functions.

[The effect of the high-molecular components of the blood serum--gamma-globulin and albumin--on the sodium channel activity of neuroblastoma cells]. / Vliianie vysokomolekuliarnykh komponentov syvorotki krovi--gamma-globulina i al'bumina--na aktivnost' natrievykh kanalov kletok neiroblastomy.

Blood serum gamma-globulin and albumin were tested for their effect on the sodium currents of voltage clamped internally perfused serum deprived neuroblastoma cells. Albumin in the concentration corresponding to its content in 5% blood serum (22 microM) produced an increase in sodium channel currents and shifts in activation and inactivation curves along the voltage axis towards more negative or positive potentials, respectively. These results both qualitatively and quantitatively reproduce the effects of 5% blood serum observed previously (Zubov, Sal'nikov, 1984, 1986). The addition of gamma-globulin failed to change the parameters registered. The data obtained led us to an assumption of the role of albumin as an active substance responsible for the effect of blood serum on the potential-dependent sodium-transporting system of neuroblastoma cell membrane.

[Effect of sodium, lithium and amiloride on the K+-dependent phosphatase activity of membrane preparations of Na,K-ATPase]. / Vliianie natriia, litiia i amilorida na K+-zavisimuiu fosfataznuiu aktivnost' membrannykh preparatov Na,K-ATFazy.

Effects of sodium, lithium and amiloride on the ATPase reaction and on its potassium-dependent step were studied using membrane preparations of Na,K-ATPase. It was established that the addition of 70 mM NaCl or LiCl to the reaction medium diminished the hydrolysis of para-nitrophenyl phosphate (pNPP) by 70 and 40%, respectively. Amiloride (0.8 mM) inhibited activities of Na,K-ATPase and pNPPase by 50 and 15%, respectively. The higher concentrations of amiloride produced a more prominent inhibition of Na,K-ATPase, but not of pNPPase. There was no correlation between the effect of amiloride on the pNPP hydrolysis and potassium concentration in the medium. There was the additivity in the inhibition of pNPPase by 0.8 mM amiloride and sodium or lithium ions up to the concentrations of ions as high as 30 mM. A conclusion is made that the inhibition of Na,K-ATPase by amiloride is mediated through the modification of the sensitivity of the enzyme to sodium.

[Effect of blood plasma and serum and its fractions on the activity of the sodium channels in neuroblastoma cells]. / Vliianie plazmy, syvorotki krovi i ee fraktsii na aktivnost' natrievykh kanalov neiroblastomy.

Blood plasma, serum and its fractions containing components of different molecular masses obtained by dialysis and gradual ultrafiltration were tested for their action on the sodium currents of voltage clamped internally perfused neuroblastoma cells. Blood plasma free of platelet factor 4, serum and its fractions containing components of molecular masses more than 50 kD produced an increase in sodium channel currents and shifts in activation and inactivation curves along the voltage axis towards more negative or positive potentials, respectively. Moreover, the serum deficient in components with the molecular masses less than 50 kD produced a more prominent effect on all the parameters tested. Thus, the low-molecular fractions were suggested to exert an inhibitory activity on the stimulatory effects produced by the high-molecular components of the serum.

[Changes in the properties of the enzymes of energy allowance resulting from heat shock in lake frogs]. / Izmenenie svoistv fermentov énergoobespecheniia ozernykh liagushek v rezul'tate teplovogo shoka.

A study was made of the activity and heat resistance of preparations of Na, K-ATPase, Mg-ATPase and succinate dehydrogenase of the lake frog R. ridibunda caused by the heat shock of animals. A decrease in the activity and an increase in the heat resistance of all the three enzymes studied were observed. The level of individual correlations between these parameters remained unchanged. An increase in the heat resistance of Na, K-ATPase occurs at the expense of a higher threshold of its thermal inactivation without changes in the affinity of this enzyme to Na+ and K+. Under discussion is the question of the functional significance of the changes observed.

[Correlations of the individual levels of the activity and heat resistance of energy-support enzymes in the lake frog]. / Issledovanie korreliatsii individual'nykh urovnei aktivnosti i teploustoichivosti fermentov énergoobespecheniia ozernoi liagushki.

A study was made of the correlation between the levels of the activity and heat resistance of Na,K-ATPase, Mg-ATPase and succinate dehydrogenase (SDG) in Rana ridibunda. A correlation was observed between the activities of two ATPases, and between either of them and the activity of liver SDG. The correlation coefficient between the heat resistance levels was statistically significant only in SDG of liver and muscles. The question whether the criterion of T50% inactivation may be good for a comparative appraisal of the heat resistance of enzymes is under discussion.

[Properties of the enzymes of energy supply in the common frog under various physiological states. II. Changes in the heat resistance of adenosine triphosphatases and succinate dehydrogenase]. / Issledovanie svoistv fermentov énergoobespecheniia travianoi liagushki pri raznykh fiziologicheskikh sostoianiiakh organizma. II. Izmenenie teploustoichivosti adenozintrifosfataz i suktsinatdegidrogenazy.

The heat resistance of SDG, Na, K-ATPase and Mg-ATPase of the grass frog was determined in January, March and May, the number of animals examined being 30-40 in either experiment. It was found that the average level of the heat resistance of the enzymes studied shows significant, often differently directed changes, which depend on the physiological state of an organism. Negligible correlation between the thermal sensitivity of different enzymes of an organism during hibernation, completely disappear during the activity state.

[Properties of the energy-allowance enzymes of the common frog in different physiological body states. I. Adenosine triphosphatase and succinate dehydrogenase activities]. / Issledovanie svoistv fewrmentov énergoobespecheniia travianoi liagushki pri raznykh fiziologicheskikh sostoianiiakh organizma. I. Aktivnost' adenozintrifosfataz i suktsinatdegidrogenazy.

The activity of SDG, Na, K-ATPase and Mg-ATPase of the grass frog was determined in January, March and May, the number of animals examined being 30-40 in either series of experiments. In May (period of reproduction) the average activity of the above enzymes was higher than in January and March. This was observed both in males and females. A correlation between enzymatic activities of each single organism in March and May significantly increased. The role of these changes in the increase of viability of the organism is discussed.

[Dependence of Na, K-ATPase enzyme activity on the surface properties and charge of the substances interacting with the cell membrane]. / Zavisimost' fermentativnoi aktivnosti Na, K-ATFazy ot poverkhnostnykh svoistv i zariada vzaimodeistvuiushchikh s kletochnoi membranoi veshchestv.

The surface activity and effect of histone, sodium deoxycholate and Triton X-100 on N+,K+-ATPase have been compared. It has been found that the coefficient of surface tightness on the borderline of suspension of ATPase containing membranes/air decreases with the increase in concentrations of these agents. The enzyme activity undergoes biphasic modification increasing with lower and decreasing with higher concentrations of the agents. The effectiveness of the agents depends on the charge of their molecules. The mechanism of interaction between Na+,K+-ATPase and the above modifiers is discussed.

[Activity and thermal stability of the enzymes of energy support in the common frog]. / Izuchenie aktivnosti i teploustoichivosti nekotorykh fermentov energoobespecheniia travianoi liagushki.

The activity and heat resistance of succinate dehydrogenase (SDG), Na, K-ATPase and Mg-ATPase of the grass frog (39 specimens) have been determined. No correlation was found between individual levels of heat resistance both of either enzyme examined and of the same enzyme but taken from different tissues (SDG of liver and muscles). The average level of heat resistance of SDG in liver is significantly higher than that in m. gastrocnemius. A statistically significant correlation was observed between individual levels of enzyme activity in the internal organs (SDG of liver, Na, K-ATPase and Mg-ATPase of kidney). The activity of SDG of muscles does not correlate with that of either partner.

[Comparison of the heat resistance of ATP-hydrolyzing enzymes in 2 species of frogs]. / Sravnenie teploustoichivosti ATF-gidrolizuiushchikh fermentov u dvukh vidov liagushek.

A comparison was made between the heat resistance levels of two enzymatic preparations: the actomyosinic and the transport ATPases of two species of frogs (grass and lake frogs) differing in their thermophilia. The interspecies differences in the heat resistance were found to be 6 degrees C for the actomyosinic and 3 degrees C for the transport ATPase in favour of the more thermophilic lake frog. In both species the myosinic ATPase is more sensitive to heat than the transport one. The high heat resistance of the transport ATPase is due to a higher threshold of its sensitivity to temperature.

[Effect of pH on ATPase activity and 18-O metabolism catalyzed by membrane preparations of Na,K-ATPase from guinea pig kidneys]. / Vliianie pH na ATFaznuiu aktivnost' i 180-obmen, kataliziruemye membrannymi preparatami na,K-ATPazy iz pochek morskoi svinki.

The effect of pH in the incubation medium on ATPase activity and the direct 18O-exchange, catalyzed by initial and treated by surface active agents membrane preparations of Na, K-ATPase has been studied. The pH dependence of the ratio between the direct 18O exchange and Na,K-ATPase activity was detected; this ratio being equal to 4,5 +/- +/- 0.6, 1.5 +/- 0.1 and 0.4 +/- 0.1 at the pH values of 6.1, 7.5 and 9.0, respectively. The pretreatment of preparations by DOC or histone H2a, used in both activatory and inhibitory-amounts, abolished the effect of acid pH and made the ratio practically the same at 6.1 and 7.5 pH values. Both agents did not affect the action of the alcaline pH value equal to 9.0. Triton X-100 was not able to change the pH dependence of the ratio.

[Effect of the structural integrity of Na,K-ATPase preparations on the ability of lithium to substitute for sodium in enzyme activation]. / Vliianie strukturnoi sokhrannosti preparatov Na,K-ATFazy na sposobnost' litiia zameshchat' natrii v aktivatsii fermenta.

The ability of Li+ to substitute for Na+ in activating ouabain-sensitive ATPase of the rat kidney was studied on three kinds of the enzyme preparation: a) crude membrane fraction, b) purified enzyme, c) tissue slices. The preparations were free of endogenous Na+ and K+. The ATPase activity of slices was estimated both biochemically and cytochemically. In slices, the extent of Li+--Na+-isomorphism was about 10-fold higher than that in the purified enzyme. It is concluded that the biochemical procedures involved in the enzyme isolation procedure cause the damage of membranes, thus decreasing Li+-affinity to the Na+-dependent site.

[Effect of surface-active agents on Na, K-ATPase from guinea pig kidneys]. / Vliianie poverkhnostno-aktivnykh veshchestv na Na, K-ATFazu iz pochek morskoi svinki.

The effect of surface active agents on the activity of Na, K-ATPase and on the direct medium 18O exchange in the membrane preparations of the guinea pig kidney has been studied. The medium 18O exchange was considered as a character of the K+-dependent stage in ATPase reaction. Low concentration of all the surface active agents were shown to stimulate, and high concentrations -- to inhibit both ATPase and medium 18O exchange. The relation between medium 18O exchange and Na,K-ATPase activity was found to be equal to 1.5 +/- 0.1. The treatment of preparations by activating amounts of the surface active agents resulted in lowering this relation up to 1.0 +/- 0.09 and 1.3 +/- 0.04 for DOC and triton X-100, correspondently, due to a stronger stimulation of ATPase activity than of medium 18O exchange. With the inhibiting amounts of triton X-100 and histone H2a, this relation did not change, but it decreased in the presence of equal amounts of DOC.

[Effect of various organic substances on the activity of the membrane preparations of Na, K-ATPase]. / Vliianie nekotorykh organicheskikh osnovanii na aktivnost' membrannykh preparatov Na, K-ATFazy.

The effect of guanidine, lisine, arginine, acetamide and urea on the activity of the preparations of Na, K-ATPase from guinea pig kidney was studied. It was established that the enzymatic activity of the preparations can be lowered by 50% by the following concentrations of the substances examined: guanidine--0.07 M, argine--0.12 M, lisine--0.30 M, acetamide--0.95 M, urea--1.05 M. There correlation among the inhibitory ability of these substances and their basis properties.

[Some properties of preparations of Na+ and k+-ATPase treated with deoxycholate]. / Nekotorye svoistva preparatov Na+, K+-ATFasy, obrabotannykh dezoksikholatom

The treatment of membrane suspension from the guinea pig kidney cortex possessing Na+, + K+ -ATPase activity with 0.20% sodium deoxycholate (DOX : protein equals 12 : 1) leads to lowering of their enzymatic activity. DOX-treated preparation can be divided into two fractions by centrigugation (1 hr - 22 000 g). The pellet has 1.5-fold higher enzymatic activity than the initial preparation and cannot be activated by small amounts of histones. The supernatant has 2-fold lower enzymatic activity than the initial preparation but in presence of small amounts of histones this activity rises to the level of the initial preparation activity. The action of DOX treatment on the membrane structure of Na+ + K+ -ATPase preparations is discussed.