The effects of near infrared radiation on rats assessed by succinate dehydrogenase activity in lymphocytes in blood smears

The biological effects of near infrared radiation (850 nm) modulated by an acoustic frequency of 101 Hz were studied. The study was conducted on rats; the effect was registered by succinate dehydrogenase activity in lymphocytes in blood smears after the administration of an activating dose of adrenaline, which simulates the state of the organism at early stages of a pathogenic action (stress). A pronounced regulating effect of infrared radiation on the activity of succinate dehydrogenase in animals that were activated by adrenaline was shown. Infrared radiation has a normalizing effect via the reduction of the degree of inhibition or activation of the enzyme induced by adrenaline and has no effect on the control animals. Thus, by modulation of the activity of succinate dehydrogenase, infrared radiation regulates energy production in mitochondria that is provided by the most potent oxidation substrate, viz., succinic acid; the effect is especially pronounced under stress.     

Hyperactivation of succinate dehydrogenase in lymphocytes of newborn rats

We measured the activity of mitochondrial succinate dehydrogenase (SDH) within cells, in media with near-physiological composition, in lymphocytes immobilized in a blood smear on glass. SDH activity was studied in newborn rats characterized by natural hyperadrenergic status and also in adult animals injected with epinephrine. In most newborns very high activities were recorded, which exceeded the activities in adults at rest 7-8-fold or 3-fold according to the conventional calculation, or more than 30- and 6-fold according to our more precise calculation. The findings support our concept about a selective interaction between adrenergic stimulation and oxidation of succinic acid. According to this concept, epinephrine and norepinephrine specifically activate oxidation of succinic acid, whereas blood micromolar concentrations of the latter stimulate the release of catecholamines (the receptor-mediated signaling effect). This interaction is half of a substrate-hormonal regulatory system responsible for connection of vegetative nervous system with oxidation in mitochondria of the innervated organs. The increase in succinate oxidation by catecholamines includes activation of the faster pathways of succinate generation than the complete Krebs cycle, in particular, the glyoxylate cycle that is shown in the newborn rats in the present study.     

Effect of adrenaline on the succinate dehydrogenase activity of peripheral blood lymphocytes of rats following exposure to ionizing radiation

In experiments with albino mongrel female rats, the influence of adrenaline on succinate dehydrogenase (SDG) activity in the peripheral blood lymphocytes of irradiated and intact animals has been investigated. Two minutes after the intraperitoneal administration of adrenaline (1 mg/kg) to intact rats SDG activity sharply rises and 3-4 min it drastically falls. In 6 to 8 min the second peak in the enzyme activity is registered. Twenty minutes after irradiation of rats in the cranio-caudal direction with a dose of 75 Gy delivered to head, the reaction to adrenaline, manifested by the rise in SDG activity, is absent.     

Nature of the activation of succinate dehydrogenase by various effectors and in hypobaria and hypoxia

1. Hepatic mitochondrial succinate dehydrogenase (succinate:(acceptor)oxidoreductase, EC 1.3.99.1) was activated by preincubation of mitochondria with four diverse classes of compounds, the dicarboxylic acids, nitrophenols, quinols (and ubiquinols) and pyrophosphates. Of the various compounds tested malonate, oxaloacetate and pyrophosphate, well-known competitive inhibitors of the enzyme, and also hydroquinone and ubiquinols were effective even at low concentrations and showed maximal stimulation in 2 min.2. Activation of succinate dehydrogenase by ubiquinol-9 and ubiquinol-10 was comparable to succinate activation in fresh mitochondria, and was much higher in the aged samples.3. Preincubation of mitochondria with succinate, 2,4-dinitrophenol, pyrophosphate and ATP also stimulated the succinate-2,2′,5,5′-tetraphenyl-3,3′-(4,4′-biphenylene) ditetrazolium chloride (NT) reductase activity, whereas malonate, hydroquinone and ubiquinol-9 were ineffective. A differential activation of the flavoprotein by the oxidized and reduced forms of ubiquinone-9 was observed, the former stimulating the reduction of NT and the latter of phenazine methosulphate-2,6-dichlorophenolindophenol.4. Repeated washing of the activated mitochondrial samples with the sucrose homogenizing medium, partially reversed the activation by effectors other than succinate. Further washing of the activated preparations after a second preincubation with succinate reverted the enzyme activity to the basal level in the case of malonate, ATP and pyrophosphate but not that of hydroquinone and ubiquinol-9.5. Increase in the activity of hepatic mitochondrial succinate dehydrogenase, but not of succinate-NT reductase, known to occur in rats exposed to hypobaria was also observed in hypoxia indicating that it is an effect of lowered O₂ tension. The enzyme activity in these “partially activated” preparations was stable to washing with the sucrose homogenizing medium and could be fully activated to the same level as in the controls showing thereby the qualitative nature of the change. On washing these succinate-activated preparations further with the medium, the “hypobaric activation” was not reversed to the basal level, whereas the “hypoxic activation” was reversed. These results suggest that the effectors responsible for the activation of succinate dehydrogenase under hypobaric and hypoxic conditions are probably different; the former may be of the ubiquinol type and the latter of the malonate type.     

Age and changes in succinate dehydrogenase activity in functionally different muscles of the young rat

The antigravitational m. triceps brachii, its antagonist m. brachialis and the muscle having a universal functional specialization--m. serratus ventralis--have been studied in 35 male rats of Wistar strain, 60-105-day-old. Succinate dehydrogenase activity is determined in muscle fibers. Changes in the muscle fibers continue after the rats reach their sex maturation. Certain stageness of the process is observed, but the division of the period into separate steps either is absent (m. brachials), or their number is not great as compared to those during the 1st--60th days after birth. The borders of the periods in the muscles studied coinside (the 70th--74th day). Although it is possible to reveal the periods and separate steps in the changes occurring in the muscle fibers and in the muscles of the animals having reached their sex maturation, nevertheless, the borders between them are not distinct, the reconstruction during this age proceeds slower and more smoothely than before the sex maturation. It is possible that in young rats after sex maturation differentiation of the muscle fibers continues and that, in its turn, stimulates further specialization of the muscles as organs. The changes in the muscle fibers revealed histochemically occur most slowly under a low static loading, and when loading of various modality (kinetic and static) are combined, they are mostly pronounced.     

Use of succinate dehydrogenase activity of lymphocytes to predict the course of the post-resuscitation period

The enzyme status of lymphocytes was studied in experiments on white male rats revived after a 4-min clinical death due to acute blood loss. It is established that the initial status of lymphocyte succinate dehydrogenase is essential for predicting cytochemical pattern and peculiarities of postresuscitation period.     

Histochemical modification of the active site of succinate dehydrogenase with N-acetylimidazole

The kinetics of acetylation of mitochondrial succinate dehydrogenase [EC 1.3.99.1] in the two fibre types (A and C) of rat gastrocnemius with N-acetylimidazole was studied by a newly modified histochemical technique. Acetylimidazole partially inactivated the enzyme, but subsequent deacetylation with hydroxylamine restored the enzyme activity completely. Inactivation of the enzyme by acetylimidazole was prevented by malonate, which is a competitive inhibitor of the enzyme. The value of the inhibition constant (Ki = 34 microM) for malonate, obtained from the dependence of the pseudo-first order rate constant of acetylation of the enzyme with acetylimidazole on the malonate concentration, was in good agreement with the Ki value (33 microM) obtained by a different method, the dependence of the initial velocity of succinate oxidation by the dehydrogenase on the substrate concentration in the presence of malonate. These findings suggest that a tyrosyl residue is located in the malonate binding site (the active site) of succinate dehydrogenase in the gastrocnemius and plays a role in substrate binding, but is not a catalytic group.     

Activation of succinate dehydrogenase by bicarbonate

Succinate dehydrogenase (SD) of mitochondria from rat liver or kidney is to a large extent in the active form as isolated, whereas SD activity of heart and skeletal muscle mitochondria can be activated as much as ten-fold over the basal activity when isolated. Incubation of the latter at 37° with bicarbonate resulted in more extensive activation of SD than when succinate was the activator. Activation by bicarbonate was not readily reversed by washing unless succinate was also present. The data indicate that bicarbonate and succinate share the same site for activation of SD. A physiological role for bicarbonate in regulation of SD activity in muscle is suggested.     

Heterogeneous chromosomal radiosensitivity of phytohaemagglutinin-stimulated human blood lymphocytes in culture

Human blood lymphocytes were irradiated with hard X-rays, stimulated with phytohaemagglutinin (PHA), and grown in presence of amethopterin to accumulate the responding cells at the GI/S boundary of the first cell cycle in vitro. After reversal of the GI/S block with exogenous thymidine, the frequencies of asymmetric chromosome exchanges in relation to the position of metaphases within the first generation mitotic wave were compared. Significant differences of aberration yields within replicate culture series were found in several experiments. A gradual increase of aberration frequencies with increasing duration of S + G2 phases was the most constant feature encountered. In addition, in two parallel series of cultures from one donor, the highest frequency of aberrations was found in samples corresponding to the shortest S+G2 phase duration. A significant contribution of selective mitotic delay of aberration-carrying cells to the distribution of aberration frequencies was excluded. Therefore, it was inferred that the results reflect a true variability of radiosensitivity among the PHA-responsive cells, probably of a discontinuos character, ranging over the ratio of two.