V. M. Petrovic

Effect of Cadmium and Selenium on the Antioxidant Defense System in Rat Kidneys

To examine effects of exogenous Cd on the kidney antioxidant defense system (AOS) and the possible protective role of Se against Cd toxicity, male Wistar albino rats (2 months old) were exposed during 30 days to oral intake of 200 ppm Cd (as CdCl2), 0.l ppm Se (as Na-selenite) or to the same doses of Cd / Se, simultaneously. Marked accumulation of Cd (23.44 +/- 0.69 micrograms/g w.m.) and marked alterations of AOS, resulting in kidney injury (renal pseudohypertrophy), were found in Cd-treated rats. Activities of total superoxide dismutase (SOC, EC 1.15.1.1), manganese-containing superoxide dismutase (MnSOD) and selenium-dependent glutathione peroxidase (Se GSH-Px, EG 1.11.1.9) were significantly reduced, whereas that of glutathione-S-transferase (CST, EC 2.5.1.18) and vitamin E (vit E) concentration were significantly increased in the kidneys of Cd-treated rats. Kidney catalase (CAT, EC 1.11.1.6) activity, ascorbic acid (AsA) and red blood cell glutathione (GSH, GSSG) levels were not markedly influenced by CD uptake. In kidneys of Se treated rats, the activities of total SOD, copper-zinc-containing superoxide dismutase (CuZnSOD) and GST were significantly increased Activities of kidney CAT and Se GSH-Px were largely unchanged, whereas significant increases of the kidney AsA and vit E concentrations occurred. In Cd + Se-cotreated rats, the kidney activities of MnSOD, CAT and Se GSH-Px, as well as vit E concentration, were the same as in controls, whereas CuZnSOD and GST activities and concentration of AsA exceeded normal values. These data indicate that Se only partially improves the AOS that is insufficient to prevent Cd-induced nephrotoxicity.

Seasonal dependence of the activity of antioxidant defence enzymes in the ground squirrel (Citellus citellus): The effect of cold

1. The activity of antioxidant defense enzymes (SOD, CAT, GSH-Px and GST) was analysed during the autumn and winter in the ground squirrel adapted to 30 degrees C and subsequently exposed to cold for 6 and 24 hr. 2. The liver CAT activity as well as the IBAT CAT and GSH-Px activities differed between animals adapted to 30 degrees C, studied in autumn, and those studied in winter. 3. MnSOD activity in the liver was increased in autumn but decreased in winter after 6 hr cold exposure reaching the control level 24 hr later. Cold exposure induced a decrease in CAT activity (except after 24 hr cold exposure in winter) and an increase in GSH-Px activity. Lower GST activity was found after 24 hr exposure to cold in winter. 4. The IBAT SOD activity decreased under the influence of cold during both seasons with a tendency to return to the control level only in winter. Cold exposure produced a decrease in GST in both seasons and CAT activity in autumn. GSH-Px activity was increased in winter only. 5. The results indicate a seasonal dependence of the activity of antioxidant defence enzymes in the ground squirrel. Seasonal influence was evidenced in animals exposed to cold as well.

Copper-Zinc Containing and Manganese Containing Superoxide Dismutase in the Ground Squirrel/Citellus Citellus/—THE Effect of Hibernation

The distribution of Copper-Zinc containing and Manganese-containing superoxide dismutase in the liver, kidney, interscapular brown adipose tissue (IBAT) and brain of the ground squirrel, as well as the effect of hibernation, was studied. Activity of both forms of SOD was highest in the liver and lowest in the brain. Activity of the Mn SOD in relation to total SOD was higher in the liver and kidney of the ground squirrel as compared with results reported for other rodents. The highest activity of Mn SOD in relation to total SOD was found in the IBAT and brain (36% and 49%, respectively). Total SOD activity per mg proteins and per g wet mass in IBAT and brain of hibernating animals was increased: for IBAT, p less than 0.05 and p less than 0.025, respectively; for brain, p less than 0.01 and p less than 0.025, respectively. Protein content in hibernating ground squirrel was not significantly changed. In the hibernating ground squirrel CuZn SOD activity in IBAT and brain was higher as compared with the active animal (p less than 0.025 and p less than 0.005, respectively). In the liver and kidney CuZn SOD was not significantly changed during the hibernation. In the liver and brain of the hibernating animals a lower Mn SOD activity was found (p less than 0.005 and p less than 0.05, respectively).

Selective effect of noradrenaline on superoxide dismutase activity in the brown adipose tissue and liver of the rat

Noradrenaline treatment results in a significant increase of superoxide dismutase activity in the intrascapular brown adipose tissue but not in the liver.

Hormones and Antioxidant Defense

The antioxidant defense system has enzymatic and nonenzymatic components. The enzymatic system consists of three basic enzymes: superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px). Nonenzymatic components are low-molecular weight compounds such as vitamin A, retinoic acid, vitamin C, vitamin E, iron chelators, glutathione and other thiols (1). The physiological role of this system is to prevent oxidative damage to cells caused by chain reactions initiated by free radicals, which are important in carcinogenesis and radiation damage, etc. Since it is not quite certain whether endogenous antioxidants really form a system, this term is often replaced by the term antioxidant defense (2), which much better reflects the current knowledge on interactions with free radicals or oxidants.

The Effect of Dexamethasone on the Antioxidant Enzymes in the Blood of Rats

In this Addendum we are presenting our results on the effect of the synthetic glucocorticoid, dexamethasone, on the activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px) and glutathione-S-transferase (GST) in the blood of the rat.

Neuroendocrine Control in the Thermal Stress

Stress may be defined in terms of any adjustment directed towards a reestablishment of internal homeo-stasis (Ganong, 1980). Starting from Selye’s terminology, stress might be defined as such a type of response in which an increased ACTH secretion occurs (see Axelrod, 19 80). However, the increased ACTH secretion and consequently an increased adrenocortical activity was also found in intensive muscular activity and swimming. In such a kind of activity if muscular work is not very intensive, the typical stress reaction of pituitary-adrenocortical system does not occur. Thus, it was suggested that at the present time a quantitative criteria for stress rather than a qualitative, should be used (Kozlowsski, 1980). Having in mind all available data about stress it seems necessary that the kind of stressor, used by different authors in order to provoke stress in laboratory animals, should be well defined. So the character and magnitude of the response to stress should be better understood.

EFFECT OF HEAT ON BIOSYNTHESIS OF MITOCHONDRIAL PROTEIN COMPONENTS AND ATPase IN THE RAT LIVER

Publisher Summary This chapter explores the effect of heat on biosynthesis of mitochondrial protein components and ATPase in a rat liver. In warm environment, animals show a decreased rate of heat production and a reduction in the enzyme activity of liver mitochondria with reduction in liver glucose-6-phosphatase activity. In an earlier study, it was found that the rate of synthesis and breakdown of cytochrome is independent of the environmental temperature. The chapter presents an experiment to obtain more precise information on the synthesis of mitochondrial protein components and ATPase activity in the liver after a short-term exposure to heat. In the experiment, the specific activity of unfractionated mitochondrial proteins was somewhat lower in heat-exposed animals than in controls.