Parameters of cerebral energy metabolism in rat breathing nitrogen- and argon-containing hypoxic mixtures

Abstract

The study explores the effects of oxygen-nitrogen and oxygen-argon hypoxic mixtures (5-6%) on energy metabolism in rats. It is shown that in animals breathing an argoncontaining hypoxic mixture oxidative phosphorylation is less affected by acute hypoxia that in animals breathing a nitrogen-containing mixture. Key Words: hypoxia; argon; nitrogenInert gases under high barometric pressure exert a pronounced biological effect: an inert-gas narcosis. Moreover, inert gases under normal and elevated pressure are not biologically inert and modulate the rate of fundamental biological processes [2,8], in particular they enhance oxygen consumption by hepato-However, we found no publications on the effect of inert gases in hypoxic mixtures on respiratory enzymes.It has been previously demonstrated that life span of rats breathing hypoxic oxygen-argon mixture containing 4% oxygen 2-fold longer than that of rats breathing hypoxic nitrogen-oxygen mixture with the same percentage of oxygen.In the present study we investigated the effect of argon on the respiratory enzymes NADH dehydrogenase (NADH-DH) and succinate dehydrogenase (SDH) in the motor cortex under hypoxic conditions. MATERIALS AND METHODSRandom-bred albino rats were divided into 4 groups (4 rats per group) and placed to an air-conditioned The chamber was then ventilated with hypoxic (7% oxygen) oxygen-argon (group l) or oxygennitrogen (group 2) mixture until oxygen content decreased to 7% and then it was maintained within 5-6%. Group 3 animals breathed air (control). Temperature in the chanber was 19-20~ content of CO 2 did not exceeded 0.4 kPa. The duration of the experiment was 1 h. Group 4 animals were intact.All animals were decapitated immediately after the experiment, heads were wrapped in aluminum foil and frozen.Activity of respiratory enzymes SDH and NADH-DH in the motor cortex was measured using a quantitative histochemical method [5]. The amount of formazan (M) formed by 1 M protein nitrogen for 1 min at 37~ was taken as one unit of enzyme activity and expressed in milliunits (raM) formazan per 1 rain. Morphological evaluation of enzyme activity was carried out. RESULTSIn group 1, SDH and NADH-DH activities after inhalation of an oxygen-argon mixture decreased by 17% in comparison with intact rats (Fig. 1).In group 2, activities of both enzymes after inhalation of nitrogen-oxygen mixture decreased by 30%,

Argon: Systematic Review on Neuro- and Organoprotective Properties of an “Inert” Gas

“…Therefore metabolism, oxygen consumption and resistance towards hypoxia under argon (different species and organ slices) were investigated [9,19,20,21]. A favorable metabolic condition with a distinct energy metabolism and elevated oxygen consumption was supposed, thus resulting in increased resistance towards hypoxia [20,22].…”