[Modulation of voltage-gated sodium channels by recombinant interferon-alpha2b in the human neuroblastoma cell line IMR-32]. / Moduliatsiia potentsiialupravliaemykh natrievykh kanalov kletok neiroblastomy cheloveka IMR-32 pri deistvii rekombinantnogo interferona-alfa2b.

Clonal human neuroblastoma cells imr-32 are a suitable model system for studies of neuronal excitability modulation. The ability interferon-alpha 2b "laferon" to modulate the mechanisms of electrical activity was studied in whole-cell patch-clamped undifferentiated human neuroblastoma cells IMR-32. It was shown that 1 h incubation of IMR-32 cells at 37 degrees C in medium with laferon (600 U/ml) exerted changes in voltage-dependent properties of Na(+)-channels. The results of the present study demonstrate that laferon decreased of Na(+)-channels sensitivity to changes of membrane potential leading of IMR-32 cells electrical excitability decrease.

[The Ca2+-activated photoprotein obelin as a calcium transport inducer in proteoliposomes in the membrane of the T-system of skeletal muscles]. / Ca2+-aktiviruemyi fotoprotein obelin kak indikator kal'tsievogo transporta v proteoliposomakh, vkliuchaiushchikh membrany T-sistemy skeletnykh myshts.

The calcium-binding photoprotein obelin extracted and purified from the luminescent hydroid Obelia longissima was used to record the processes of Ca2+ release from proteoliposomes. It has been shown that lecithin proteoliposomes with incorporated rabbit skeletal muscle T-system membranes possess a BAY K-8644-activated permeability which is inhibited by nitrendipine. The Ca(2+)-activated photoprotein obelin is a convenient and perspective tool in studies of fast calcium fluxes.

[Calcium transport in proteoliposomes incorporating membranes of skeletal muscle T-system]. / Izuchenie kal'tsievogo transporta v proteoliposomakh, vkliuchaiushchikh membrany T-sistemy skeletnykh myshts.

Using the radioisotope method, the Ca2+ transport through proteoliposomes was investigated. The proteoliposomes originating from total brain lipids and skeletal muscle T-system membranes of the rabbit were shown to possess a Ca2+ permeability which can be stimulated by 1.4-dihydroxypyridine derivatives (10(-9)-10(-7) M). Verapamil and Cd2+ (10(-5) M and 10(-3) M, respectively) inhibit the Ca2+ permeability of proteoliposomes stimulated by dihydroxypyridine derivatives. The activating effect of the latter depends on the microviscosity of the proteoliposome lipid bilayer. An addition of cholesterol to brain phospholipids at a ratio of 1:5 increases the stimulating effect of dihydroxypyridine by 50%.

[Effect of amiloride on the activity of membrane-bound and soluble Na+-,K+-ATPase preparations]. / Vliianie amilorida na aktivnost' membranosviazannogo i rastvorimogo preparatov Na+-,K+-ATPazy.

Amiloride (8 X 10(-4), an inhibitor of sodium channels of nonexcited membranes, inhibits the activity of Na+,K+-ATPase in the kidney cortex homogenate as well as that of the partially purified membrane-bound and lubrol-soluble Na+,K+-ATPase preparations from the cattle brain. Inhibition of Na+,K+-ATPase from different organs of various animals by amiloride, a blocker of sodium channels, indicates similarity of the molecular organization of the Na+-recognizing component both of sodium channels and sodium centres of Na+,K+-ATPase.

[Incorporation of Na,K-ATPase into human erythrocyte membranes using liposomes]. / Vstraivanie Na,K-ATPazy v membrany éritrotsitov cheloveka s pomoshch'iu liposom.

A procedure for incorporation of isolated cattle brain Na,K-ATPase into erythrocyte membranes by proteoliposomes has been elaborated. The Na,K-ATPase activity of proteoliposome-treated human erythrocytes containing incorporated Na,K-ATPase does not exceed that of control erythrocytes. In the erythrocyte membrane the incorporated enzyme exists in a functionally active state and retains the vector properties of the Na+-pump. Exogenous ATP stimulates 22Na influx and 86Rb efflux in and from the erythrocytes.

[Lipid composition of different preparations of brain Na+, K+-ATPase]. / Lipidnyi sostav razlichnykh preparatov Na+, K+ -ATP-azy golovnogo mozga.

The content and composition of phospholipids is determined in beef microsomal and synaptosomal fractions and also in these fractions preparations solubilized with triton X-100 (0.1%) and digitonin (0.2%). It is shown that the microsomal fraction is richer in phospholipids. The solubilized fragments of microsomes have less or the same amount of phospholipids per protein unit than the initial fraction of microsomes, and the solubilized fragments of synaptosomes contain a higher quantity of phospholipids than the initial fraction. The content of phospholipids in "the riton" fragments of synaptosomes is higher than in "those" of microsomes. Contrary to digitonin which solubilizes the active Na+, K+-ATPase complex of microsomes and synaptosomes, triton X-100 solubilizes the active enzyme of microsomes only. A higher total content of phospholipids in "the triton" extracts of synaptosomes does not probably correlate with the presence of Na+, K+-ATPase activity in them. But these extracts are found to contain less phosphatidylserine whose addition recovers Mg2+, Na+, K+-ATPase activity in them. The effect of phosphatidylserine is not strictly specific for "the triton" extracts of synaptosomes, this lipid activates to a definite extent the extracts of microsomes as well. It is shown that at the first stages of bull brain Na+, K+-ATPase purification the total content of phospholipids and cholesterol in the preparations increases but the composition of phospholipids remains unchanged.

[Sodium pump reconstruction in lipid vesicles]. / Rekonstruktsiia natrievogo nasosa na lipidnykh vezikulakh.

Reconstitution of purified lubrol-solubilized preparation of Na,K-ATPase from the calf brain was performed in liposomes and transport characteristics of this system were investigated. The system was demonstrated to preserve vectoral features of the sodium pump. Addition of ATP to the medium evoked active influx of sodium and efflux of rubidium in proteoliposomes. Ouabain inhibited transport processes when enclosed into proteoliposomes, i.e. from the side opposite to the ATP-sensitive one.

[Study of ADP effect on brain Na+, K+-ATPase]. / Izuchenie vliianiia ADP na Na+, K+- ATPazu mozga

A mechanism of K-insensitive, ouabain-dependent liberation of Na+ from the cell during an increase in ADP intracellular concentration is studied. It is shown that the increase in the ADP/ATP ratio does not change the Na+, K+-ATPase affinity to K+ ions and does not result in the Na-activated, K-independent ATPase reaction. ADP protects ATPase from the inhibition by ouabain which is accounted for by a decrease in the concentration of a glycoside-sensitive form of the enzyme E2-P due to a turnover of the phosphokinase step of the reaction, but not due to the binding of free Mg2+ ions. The results obtained suggest that the increase in ADP concentration within the cell activates Na-Nan exchange along Na-transporting channels of the ionic pump.