[Morphofunctional preservation of rat liver mitochondria incubated at 0 degrees C]. / Morfofunktsioanl'naia sokhrannost' mitokhondrii pecheni krysy v khode inkubatsii pri 0 gradusa C.

Studies have been made on the valinomycin-induced transport of Cs+ at 0 degree C in rat liver mitochondria energized with succinate. Under these conditions, mitochondria preserve their ability to accumulate Cs+ for 6 hours of incubation or even longer. The rate of both the inward and outward movement of Cs+ at 0 degree C was approximately an order lower than at room temperature, although the stationary distribution of Cs+ remained at a high level. Electron microscopic observations revealed no significant changes in the structure of mitochondria in spite of their prolonged incubation. These properties of mitochondria make it possible to determine the kinetic parameters of ion transport and in this way to evaluate functional condition of mitochondria at low temperatures.

[Active transport of triphenylmethylphosphonium in mitochondria]. / Aktivnyi transport trifenelmetilfosfoniia v mitokhondrii.

Energy-dependent accumulation of triphenylmethylphosphonium (TPMP+) in rat liver mitochondria at 0 degree C is only 30-50% less than that observed at room temperature, while the rate of TPMP+ penetration drastically decreases enabling accurate studying of transport kinetics. Potassium diffusion potential accelerates the influx of TPMP+ and decreases the efflux rate in agreement with the expected behaviour of penetrating cations diffusing along or against an electric field. On the contrary, energization of mitochondria supposed to generate the metabolic membrane potential increases only the influx rate of TPMP+ without affecting the efflux of the cation. The data are clearly inconsistent with the presence of a metabolically dependent membrane potential. Energy-dependent accumulation of TPMP+ appears to be an active process transporting lipophilic cations against their electrochemical gradient. Stationary-state distribution of TPMP+ between energized mitochondria and medium cannot be used for the membrane potential determination.

[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.

[Extraction of lithium ions from fresh water by Lampetra fluviatilis lampreys and Oncorhynchus nerka salmon in natural ecosystems]. / Izvlechenie ionov litiia iz presnoi vody minogoi Lampetra fluviatilis i lososem Oncorhynchus nerka v estestvennykh ékosistemakh.

Some theoretical criteria are discussed which allow, using the data on the dynamics of natural concentrations and the rate of excretion of elements (ions) in aquatic animals during prolonged starvation, to establish the presence or absence of direct uptake of these elements from water under natural conditions. During pre-spawning starvation of the lamprey Lampetra fluviatilis and salmon Oncorhynchus nerka, it was shown that they are capable to accumulate Li+, similarly to Na+, directly from the fresh water. Natural concentrations of Li+ in muscles, measured mass-spectrometrically using isotope dilution, vary in the lamprey within 0.3-0.6 muequiv./kg, and in spite of the rapid excretion of this ion by the kidneys, are not decreased within a 7-month starvation; in the salmon from the lake Dal'nee (Kamchatka) they vary within 0.1-0.2 muequiv./kg. The period of semi-exchange of Li+ in lampreys in fresh water is equal approximately to 1 day.