Specific Features of Immediate Ultrastructural Changes in Brain Cortex Mitochondria of Rats with Different Tolerance to Hypoxia under Various Modes of Hypoxic Exposures

Abstract

We performed ultrastructural study of cerebral cortex mitochondria in rats with different tolerance to oxygen deficiency (low resistant and highly resistant specimens). Low resistant rats were characterized by the prevalence of mitochondria with lightened matrix due to the nondense packing of cristae. By contrast, mitochondria of highly resistant animals had the dense packing of cristae. The structure of mitochondria underwent adaptive changes at 14-10% O in the inspired air. Under these conditions, structural characteristics of the cerebral cortex in hypoxia-sensitive rats resembled those in resistant animals. The decrease in O concentration to 8% was accompanied by ultrastructural signs of mitochondrial damage, which correlated with de-energization of the cell and dysfunction of adaptive signaling systems. Ultrastructural features of cerebral cortex mitochondria in animals with low and high tolerance to acute oxygen deficiency confirm the hypothesis that they are associated with two different "functionaland-metabolic portraits".

Mitochondrial KATP Channel Function under Hypoxia

“…It is worth mentioning that higher adaptive capacities of the animals to hypoxia coincided with higher mKATP channel activity [28,29], which implies the role of mKATP channel in the modulation of mitochondrial dynamics and agrees with supposed role of the channel in the adaptation to hypoxia.…”

“…Adaptive changes after exposure to 10-14% O 2 were also observed in cerebral cortex mitochondria [29]. More dense cristae package was found in the animals showing higher adaptive capacities to hypoxia [29]. It was observed too that short-term hypoxia exposure promoted mitochondrial division, thereby greatly increasing the number of mitochondria due to the formation of new microorganelles [10].…”

“…Also, hypoxia exposure resulted in moderate swelling of cardiomyocyte mitochondria (by 25% from the initial diameter) and the formation of vesicular cristae [10]. Adaptive changes after exposure to 10-14% O 2 were also observed in cerebral cortex mitochondria [29]. More dense cristae package was found in the animals showing higher adaptive capacities to hypoxia [29].…”

Differences in Tolerance to Hypoxia: Physiological, Biochemical, and Molecular-Biological Characteristics

“…Clinical and pathophysiological studies, focused on the research on the effect of high-altitude conditions on the organism, made it possible to distinguish two polar groups of laboratory animals and humans according to their ability to adapt to the lack of oxygen and differences in their basic resistance to hypoxia [ 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 ]. In experimental studies, according to the results of the survival time (the time before respiratory disturbances and signs of asphyxia appear) in an assessment under conditions of hypobaric hypoxia, animals are divided into tolerant and susceptible to oxygen deficiency.…”

“…Oxygen deficiency is one of the key factors in the development of infectious, inflammatory, and tumor diseases [ 1 , 2 , 3 , 4 , 5 , 6 ]. It is known that basic tolerance to hypoxia in humans and various animal species differs [ 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 ]. The differences in basic tolerance to oxygen deficiency can determine the predisposition to the development of hypoxia-related disorders.…”