Detection of borderline dosage of malathion intoxication in a rat's brain

OBJECTIVE

Humans and other animals are liable to expose to low doses of malathion (MAL). However, experimental studies on its toxic threshold dose and toxic low-dose effects have not been conducted. The aims of this study were to detect the initiation of the toxic effects of sub-acute low doses (2.5, 5, and 10 mg/kg) of MAL by immunohistochemical and biochemical parameters in rat brain.

MATERIALS AND METHODS

Twenty-eight rats were randomly assigned into four groups (n=7) including control and three different amounts of MAL-exposed groups (2.5, 5, and 10 mg/kg).

RESULTS

On immunohistochemical examination, the number of caspase-3-positive cells in all MAL-exposed groups was significantly higher than in the control group. Consistent with this, the total antioxidant capacity, total oxidant status, and the levels of superoxide dismutase, malondialdehyde, and paraoxanase activity were significantly different in the 5 and 10 mg/kg MAL-exposed groups compared with the control group. Additionally, the total oxidant status and malondialdehyde levels were significantly higher in the 5 and 10 mg/kg MAL-exposed groups compared with those in the 2.5 mg/kg MAL-exposed group.

CONCLUSIONS

Our results indicate that over 5 mg/kg MAL exposure may result in dose-dependent oxidative stress, increased caspase-3 activity, and launching to the toxic effects in rat brain.

Assesment the role of oxidative stress and efficacy of caffeic acid phenethyl ester (CAPE) on neurotoxicity induced by isoniazid and ethambutol in a rat model

OBJECTIVE

The aim of this study were to investigate a role of oxidative stress and the therapeutic efficacy of caffeic acid phenethyl ester (CAPE) in the pathogenesis of neurotoxicity induced by isoniazid and etambutol in a rat model.

MATERIALS AND METHODS

Male Sprague-Dawley rats were randomly divided into eight experimental groups: control, INH, ETM, INH+ETM, INH+CAPE, ETM+CAPE, INH+ETM+CAPE, and CAPE treatment group, with ten animals in each group. INH and ETM doses were given orally within tap water for 30 days. CAPE was administered into relevant groups intraperitoneally for 30 days. Brain tissue and sciatic nerve were removed for biochemical and histopathological investigation.

RESULTS

In the INH, ETM, and INH+ETM groups, malondialdehyde (MDA) and total oxidant status (TOS) levels were significantly higher than those of the control group (p < 0.05). Also, in these groups, brain total antioxidant capacity (TAC) levels, and superoxide dismutase (SOD) and PON-1 activities were decreased compared with the control group (p < 0.05). By a CAPE supplement within INH and ETM groups, there was a significant decrease in MDA and TOS (p < 0.05). In addition to a significant increase in TAC levels, and SOD and PON-1 activities both in brain and sciatic nerve tissues (p < 0.05).

CONCLUSIONS

CAPE may protect against INH- and ETM-induced neurotoxicity in rat brain and sciatic nerve.

Impairment of endothelium-dependent vasorelaxation in cadmium-hypertensive rats

Abnormalities in the production and/or release of relaxing factors from the endothelium have been implicated in the development of hypertension in several animal models. Endothelium-dependent relaxation has been reported to be impaired in thoracic aorta in experimentally induced and genetically hypertensive rats. Present study has extented these observations to thoracic aorta of cadmium-hypertensive rats. The possible role of alterations in oxidant status was also studied. Hypertension was induced by the intraperitoneal administration of 1 mg/kg/day cadmium for 15 days. Mechanical responses produced by acetylcholine (ACh, 10— 9—10—4 M) and sodium nitroprusside (SNP, 10—10—10— 5 M) were studied on phenylephrine-precontracted thoracic aorta rings from control and cadmium-hypertensive rats. Serum nitric oxide (NO) and aortic malondialdehyde (MDA) levels were measured. ACh-induced relaxation was attenuated in aorta from cadmium-hypertensive rats, whereas relaxation responses to SNP did not differ significantly between the groups. Exposure of aortic rings to NG-nitro-L-arginine methyl ester (L-NAME, 10 —4 M) resulted in a significantly greater inhibition of relaxation response to ACh in aortic rings of cadmium-hypertensive rats as compared with control rats. Incubation with L-arginine (L-Arg, 10 —3 M) caused a similar reversal of the inhibition of ACh-induced relaxation by L-NAME in both groups. Serum NO levels were decreased and aortic MDA levels were increased in cadmium-treated rats as compared with control rats. However, the differences between the groups did not reach a statistical significance. These findings suggested that the reduction in endothelium-dependent relaxation may play a role in cadmium-induced hypertension as it was in many other hypertension models.

Protective role of caffeic acid phenethyl ester and erdosteine on activities of purine-catabolizing enzymes and level of nitric oxide in red blood cells of isoniazid-administered rats*

The aim of this experimental study was to investigate the possible role of nitric oxide (NO) and the activities of adenosine deaminase (ADA) and xanthine oxidase (XO) in the pathogenesis of isoniazid (INH)-induced oxidative damage in red blood cells (RBCs), and also to show the effect of caffeic acid phenethyl ester (CAPE) and erdosteine, antioxidants, in decreasing this toxicity. A total of 25 adult male rats were divided into four experimental groups as follows: control group ( n = 7), INH-treated group ( n = 6), INH + CAPE–treated group ( n = 6), and INH + erdosteine–treated group ( n = 6). INH, INH-CAPE, and INH-erdosteine–treated groups were treated orally with INH 50 mg/kg daily and with the tap water for 15 days. Control group was given only tap water. CAPE was intraperitoneally injected for 15 days at a dose of 10 μmol/kg. Erdosteine was treated orally for 15 days at a dose of 10 mg/kg/day. The injection of INH led to a significant increase in the activities of ADA, XO, and NO levels in RBCs of rats. Co-treatment with CAPE caused a significant decrease in the activities of ADA and XO and the levels of NO in RBCs. In addition, co-treatment with erdosteine caused a significant decrease in the activities of ADA and XO and the levels of NO in RBCs. The results of this study showed that ADA, XO, and NO may play an important role in the pathogenesis of INH-induced oxidative stress in RBCs. CAPE and erdosteine may have protective potential in this process and they may become a promising drug in the prevention of this undesired side effect of INH.

Red blood cell rheological alterations in hypertension induced by chronic inhibition of nitric oxide synthesis in rats

Nitric oxide (NO) plays a major role in vascular regulation. Modulation of NO synthesis is known to influence blood pressure. Inhibition of NO synthesis by NG-nitro-L-arginine methyl ester (L-NAME; 72 mg/kg/day, p.o., 21 days) resulted in 60% increase in blood pressure in rats. Red blood cell (RBC) transit time measured by the cell transit analyzer increased significantly in the L-NAME treated group, in comparison to normotensive rats. RBC aggregation measured in autologous plasma, by a photometric rheoscope also increased significantly in the hypertensive rats. RBC cytosolic free calcium concentration was also significantly higher in the hypertensive animals. Incubation of RBC from hypertensive and control animals with NO donor, sodium nitroprusside (SNP; 10-1000 microM) for 60 minutes resulted in a dose-dependent decrease in RBC aggregation, however aggregation index was significantly higher in hypertensive group at each SNP concentration. Incubation with SNP had no effect on RBC deformability in the control group, while a slight decrease in RBC transit time was observed only at 10 microM SNP in the hypertensive group. These results imply that NO may play a role in the regulation of rheological properties of RBC and the alterations in these properties may at least in part be involved in the development of L-NAME induced hypertension.

Tissue and blood levels of zinc, copper, and magnesium in nitric oxide synthase blockade-induced hypertension

The aim of this study was to determine the levels of tissue and blood zinc (Zn), copper (Cu), magnesium (Mg) in nitric oxide (NO) synthase blockade-induced hypertension. A group of albino rats received a NO synthase inhibitor, N(G)-nitro-L-arginine-methyl ester (L-NAME, 60 mg/kg/d) in their drinking water for 21 d. L-NAME intake caused a progressive rise in this group's resting mean arterial blood pressure compared to a control group (p < 0.01). There were no differences between the groups with regard to tissue and blood levels of Zn or Cu; however, Mg concentrations were significantly lower in the hypertensive rats' erythrocytes (20.2% reduction from control levels), cerebral cortex (17.0%), heart (9.1%), renal cortex (12%), renal medulla (16.7%), and in the tissues of the caval vein (23.7%), mesenteric artery (29.8%), renal artery (18.4%), and renal vein (22.1%). There were no significant Mg concentration changes in the hypertensive group's plasma, cerebellum, liver, duodenum, or aortal tissue. These findings suggest that Mg depletion may play a role in the blood pressure rise that occurs in the model of chronic NO synthase inhibition-induced hypertension.

Effects of diabetes on non-adrenergic, non-cholinergic relaxation induced by GABA and electrical stimulation in the rat isolated duodenum

1. The effects of streptozotocin (STZ)-induced experimental diabetes on nitrergic-mediated responses to GABA and electrical field stimulation (EFS) have been evaluated in rat isolated duodenum. 2. In the presence of noradrenergic and cholinergic blockade, EFS (60 V, 1 ms, 0.1-32 Hz) induced frequency dependent relaxations of the preparation. GABA also caused submaximal relaxation of the rat duodenum. The relaxations induced by GABA and EFS were reduced in duodenal tissues from diabetic rats compared with control rats. 3. Neither ATP- nor sodium nitroprusside-induced relaxations were altered in diabetic duodenal tissues. GABA- and EFS-induced relaxations were inhibited by NG-nitro-L-arginine methyl ester (L-NAME; 300 mmol/L) in both diabetic and control rats. Although the inhibition caused by L-NAME of GABA- and EFS-induced relaxation was partially reversed by L-arginine (1 mmol/L), L-arginine alone had no effect on GABA- and EFS-induced relaxation in diabetic rats. 4. These results suggest that STZ-induced diabetes impairs non-adrenergic, non-cholinergic relaxation induced by EFS and GABA. Impairment of nitrergic innervation of the rat duodenum may contribute to the abnormalities of intestinal motility abnormalities associated with diabetes.