[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.