An international team of scientists has found that naked mole rats are able to turn into "plants", surviving in conditions that are fatal to many other animals. "Lenta.ru" tells how these strange mammals, resembling insects, manage to change their metabolism and withstand an oxygen-free environment.
Hairless mole rats (Heterocephalus glaber) are African animals that in some ways resemble insects more than mammals. Like ants and bees, they create eusocial colonies that have a prolific queen and sterile workers. These cold-blooded and almost blind rodents dig underground tunnels, the total length of which reaches several kilometers. Passages connect living cells, storerooms and latrines. Animals communicate with each other by sound signals, their "language" is richer than that of other rodent species.
Many have heard that naked mole rats do not get cancer. In fact, this is not entirely true: malignant tumors form in them, but this rarely happens. For the first time, cancer in H.glabe was discovered last year by American scientists - two cases of the disease were reported at the National Zoo in Washington and the Brookfield Zoo in Illinois. This gave the scientists information that naked mole rats are not one hundred percent protected from carcinogenesis, although it is believed that it was the content in captivity that provoked the development of dangerous neoplasms.
According to some researchers, the resistance to cancer in these underground rodents is due to their lifestyle. The fact is that naked mole rats live in an environment with a relatively low oxygen content (2-9 percent), while humans breathe air with an oxygen content of 21 percent. This should somehow activate anti-tumor protection, although there is no confirmation of this hypothesis yet.
However, the hypoxia in which naked mole rats live is responsible for another unusual property of these animals. Their skin is insensitive to the acid and burning substance capsaicin (found in pepper). Why do animals need such adaptation, which almost never get to the surface? The fact is that carbon dioxide accumulates in the underground passages. When it dissolves in water, carbonic acid is formed, which can cause burning in rodents on moist mucous membranes. To live comfortably in such conditions, H.glabe partially loses pain sensitivity ("Lenta.ru" wrote about this).
Naked mole rats can withstand high concentrations of carbon dioxide for long periods of time. They do not react in any way if the CO2 inside the hole reaches 7-10 percent, do not try to go to places more saturated with oxygen; they have no signs of pulmonary hyperventilation and tissue acidosis. They survive for five hours, even when the carbon dioxide concentration is 80 percent (the oxygen concentration is 20 percent).
Photo: Thomas Park / UIC
How can naked mole rats survive underground, where there is so little oxygen? In fact, these rodents look like not only insects, but also plants. Under conditions of O2 deficiency, blind mammals change their metabolism by starting to break down fructose anaerobically. This process produces enough energy for brain cells to prevent their death.
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Scientists placed naked mole rats inside atmospheric chambers and recreated hypoxic conditions. The oxygen concentration was five percent. Underground rodents did well for five hours, and normal mice (Mus musculus) died in less than 15 minutes. But the researchers didn't stop there. They completely deprived the chamber of oxygen, as a result of which the mice could not stand even a minute. The naked mole rats lost consciousness after 30 seconds, but attempts to breathe continued for several minutes. Eventually, breathing stopped, but as soon as they were transferred to room conditions, H.glabe revived and showed no signs of brain damage. The rodents survived after 18 minutes in a completely oxygen-free environment.
Photo: Public Domain / Wikimedia
Scientists have found that with prolonged hypoxia, large amounts of fructose and sucrose (a disaccharide that contains fructose) enter the blood of animals. Carbohydrates enter rodent brain cells using molecular pumps that were previously only found in the intestines of other mammals. Fructose is metabolized through a process called glycolysis, which normally involves glucose.
However, glucose cannot be used due to the fact that one of the stages of glycolysis requires the presence of an active enzyme called phosphofructokinase-1. Its functioning depends on the energy state of the cell, which is greatly impaired without oxygen. As a result, the entire cycle of glycolysis stops, and the cell completely loses the ability to produce the energy necessary for life. Fructose allows you to bypass this barrier. This produces lactate (lactic acid) and energy production, albeit in small amounts, occurs at a high rate.
This ability to switch metabolism to survive in harsh conditions is common in plants, but not in mammals, the researchers said.
The scientists hope that their discovery will lead to the development of new methods to prevent damage to cardiac tissue due to hypoxia associated with coronary heart disease.
Alexander Enikeev