Study of the Antihypoxic Activity of a New Benzimidazole Derivative with Dicarboxylic Acid under Histotoxic Hypoxia

The antihypoxic activity of a new benzimidazole derivative with dicarboxylic acid under histotoxic hypoxia was studied. It was established that the studied pharmacological agent at a dose of 25 mg/kg increases the life expectancy of animals by 2 times compared with the control group, 1.3 times compared to ethylthiobenzimidazole hydrochloride and 1.2 times compared to ethylmethylhydroxyperidine succinate.

The influence of new coumarin derivatives on survival rate of mice in model conditions of acute hypoxia

Objective. The article is devoted to study the anti-hypoxemic properties of new coumarin derivatives in the models of hypoxemic hypoxia with hypercapnia, hemic hypoxia and histotoxic hypoxia. Materials and methods. Нypoxemic hypoxia with hypercapnia was modeled as follows: mice were placed in hermetic 200 cm3 jars one in a jar. Hemic hypoxia was reproduced in mice by single subcutaneous introduction of sodium nitrite in a dose of 230 mg/kg. Histotoxic hypoxia was caused in mice by intraperitoneal introduction of sodium nitroprusside in a dose of 20 mg/kg. Coumarin derivatives under lab codes IEM-2266 and IEM-2267 were dissolved in distilled water with addition of twin-80, and then a single intraperitoneal infusion of them in doses 25 and 50 mg/kg was made 45 minutes before placing to the model conditions. Increased life time of an animal compared with the control served the criterion of anti-hypoxemic effect of the studied substances. Results. In hypoxemic hypoxia with hypercapnia test compound under IEM-2267 in doses of 25 and 50 mg/kg increased mice life time by 26 and 34% respectively in comparison with control. In hemic hypoxia model, the positive effect was seen with IEM-2266 compound in a dose of 50 mg/kg which increased life time of animals by 45% in comparison with control. In histotoxic hypoxia model, at preventive introduction of IEM-2266 compound in a dose of 25 mg/kg and IEM-2267 in a dose of 50 mg/kg life time increased up to 117% and 123% respectively. Conclusion. The coumarin derivatives IEM-2266 and IEM-2267 relieved the course of acute hypoxia and increased life time of animals in the models of hypoxemic hypoxia with hypercapnia, hemic hypoxia and histotoxic hypoxia.

ANTI-HYPOXIC ACTIVITY OF THE NEW COMPLEX COMPOUND OF OXYMETHYLURACIL WITH SODIUM SUCCINATE

On the models of acute hemic and acute histotoxic hypoxia, the activity of a new complex compound of 5-hydroxy- 6-methyluracil with sodium succinate was studied. It was found out that the compound under investigation in respects to its activity is comparable or superior to reference preparations-reamberin, sodium succinate and oxymethyluracil, and has low toxicity at intragastric and intraperitoneal administration to mice. Based on the results of the studies, the patent of the Russian Federation was awarded.

Absence of Hydrogen Sulfide-Induced Hypometabolism in Pigs: A Mechanistic Explanation in Relation to Small Nonhibernating Mammals

Artificially induced hypometabolism in nonhibernating mammals may have considerable clinical implications. Numerous studies in small rodent models have demonstrated that hydrogen sulfide (H2S) induces hypometabolism, supposedly as a result of histotoxic hypoxia. However, the induction of hypometabolism is absent in large animals following H2S administration. To determine the cause of this animal size-dependent discrepancy in H2S pharmacodynamics, the effects of sodium H2S (NaSH; 5 mg/kg/h, 4-hour intravenous administration) on systemic, pneumocardial, hematological, biochemical, microvascular (sublingual), and histological parameters were investigated in pigs. After 4 h, no differences were observed between the NaSH and control group with respect to systemic, pneumocardial, hematological, biochemical, and histological parameters. However, NaSH triggered significant hyperperfusion in the sublingual microcirculation, as evidenced by an increased blood vessel diameter (154 ± 16 and 85 ± 25% vs. baseline for NaSH and NaCl, respectively), total vessel density (139 ± 18 and 98 ± 13%, respectively), and perfused vessel density (139 ± 18 and 99 ± 13%, respectively). These phenomena are consistent with microvascular changes that occur during a panting response, an important heat loss mechanism (i.e., thermoregulatory effector) in pigs that is controlled by the thermoneutral zone (Ztn). On the basis of our findings and the literature, a mechanistic explanation is provided for the differential manifestation of hypometabolism between small and large animals. In large animals, H2S does not act via histotoxic hypoxia but likely triggers carotid bodies to transmit a hypoxic signal, which subsequently lowers the Ztn and activates heat loss mechanisms (e.g., panting) to align ATP consumption with ATP production through hypothermia. Since large animals have a small surface:size ratio, the cooling rate is too inefficient to accommodate hypothermia and subsequent hypometabolism. This is why large animals do not exhibit hypometabolism, despite the activation of thermoregulatory effectors. This is also a reason for the poor translatability of artificial hypometabolism to the clinical setting.

THE EFFECT OF ADVANCE HYPOXIC TRAINING UPON TISSUE OXYGEN TENSION IN THE TUMOR DURING AQUTE HYPOXIA OF DIFFERENT TYPES

The tumors of rats who had not been acclimated to hypoxia subjected to acute hypoxic hypoxia (altitude chamber) as well as blood hypoxia (carbon monoxide) decreased tissue oxygen tension while histotoxic hypoxia (NaCN) on the contrary increased tissue oxygen tension. The tumor acclimated to hypoxia seems to select compensatory mechanisms mostly associated with increased tissue oxygen tension thus taking advantage of lower extent of tissue oxygen tension when subject to acute hypoxic hypoxia than in femoral muscle. All types of acute hypoxias caused a decrease of tissue oxygen tension in the malignancy.