[New findings on the mechanism of action of blocking toxins on electrically excitable sodium channels]. / Novoe o mekhanizme deistviia toksinov-blokatorov na élektrovozbudimye natrievye kanaly.

The paper summarizes the results obtained from the 10-12 years studies on the mechanism of action of blocking toxins--tetrodotoxin (TTX) and saxitoxin (STX)--on voltage-operated sodium channels. Experimental data can be interpreted on the basis of two models of blocking action of toxins: channel blockade, when guanidine group of toxins penetrates into the channel and causes its blockade and allosteric action on sodium conductance. Special attention is devoted to peculiarities of cooperative interaction between the blockers and channels. The analysis of experimental findings permits a better understanding of functional organization of sodium channels, in particular, the interrelation between the receptor of blocking toxins and its other structural elements.

[Temperature-independence of the effect of osmotic pressure on the inward sodium current in the membrane of isolated spinal ganglion neurons of the rat]. / Nezavisimost' vliianiia osmoticheskogo davleniia na vkhodiashchii natrievyi tok v membrane izolirovannykh neironov spinal'nykh gangliev krys ot temperatury.

The temperature dependence of the effect of transmembrane osmotic pressure on sodium TTX-sensitive inward current was studied on isolated neurons of rat dorsal root ganglia using intracellular perfusion under voltage clamp conditions. It was found that the effect of transmembrane osmotic pressure on the kinetic parameters of sodium current does not depend on temperature in a wide range (from 8 to 40 degrees C). The apparent values of activation energies for the activation and inactivation processes do not depend on osmolality. The overall results indicate that the most satisfactory way to account for the present observations is to postulate that the effect of transmembrane osmotic pressure is determined by the water flux crossing the membrane. It is supposed that this flux takes place within the protein molecule which forms the sodium channel. The molecular mechanisms of interaction between water pathways and gating are discussed.

[Properties of lipid bilayer membranes modified by brain Na+,K+-ATPase subunits]. / Svoistva bisloinykh lipidnykh membran, modifitsirovannykh sub''edinitsami Na+,K+-ATPazy mozga.

Large (alpha) and small (beta) subunits (SU) of the enzyme were obtained from the high-purified Na+, K+-ATPase preparations of the cattle brain. Molecular masses of the subunits (95 and 55 kD, respectively) have been determined and the properties of bilayer lipid membranes (BLM) modified by them were investigated. The both proteins are capable of inducing the channel conductivity in BLM which is selective to alkaline metals ions in case of alpha-SU, alpha-SUE modified BLM possess some properties of Na+, K+-ATPase: the cardial glucosides at large and small doses have a specific action, the action of the above glycosides and vanadate differs; vanadate intensifies the inhibitory effect of ouabain; the cardial glycosides and K+ have an antagonistic action; the effect of ouabain depends on the content of Ca2+ in the medium. At the same time other properties of this enzyme (dependence on ATP, magnesium ions, etc.) are not manifested with introduction into BLM. It is supposed that the ability of Na+, K+- ATPase subunits to form channel-like current fluctuations in BLM is a property of the obtained proteins and it is not obligatory realized in the processes of active K+ and Na+ transmembrane transfer.

[Ionophore properties of peptide fragments of brain Na+,K+-Atpase]. / Ionofornye svoistva peptidnykh fragmentov Na+,K+-ATPazy mozga.

Polypeptide fragments from Na+, K+-ATPase of cattle brain are obtained by the bromocyan-treatment of the protein and subsequent gel filtration via sephadexes; the fragments were reconstructed into bilayer lipid membranes (BLM). Polypeptides of fractions I and II induce cationic and polypeptides of fraction IV--cationic-anionic conductivity of BLM. Neither sodium nor potassium selectivity of BLM modified by protein fragments of fractions I and II was observed. Fluctuations of the modified membranes current are of spasmodic character, ATP and inhibitors of the sodium pump do not affect them. The induction of current fluctuations peculiar to channels into BLM is supposed to be a character of polypeptides obtained after the ATPase splitting but not of the cation-transport system of the sodium pump.