Hypoxic Preconditioning Eliminates Differences in the Innate Resistance of Rats to Severe Hypoxia

Hypoxic preconditioning is able to increase the body’s resistance to hypoxic/ischemic stress. Understanding how to apply the hypoxic response to initiate the protective mechanism of ischemic preconditioning is a high priority. However, the relationship between innate resistance to hypoxic stress and preconditioning efficiency of moderate hypoxia has been poorly studied. In our work, the efficiency of single moderate hypobaric hypoxia (HBH) for resistance to severe hypobaric hypoxia (SHBH) was studied on intact rats and those pre-tested under SHBH with low, intermediate and high resistance to hypoxia. HBH has a significant preconditioning action on the resistance to hypoxia over a wide range from 270 to 1464 s (4.5 to 24.5 min) and at the same time eliminates the differences in the endurance under SHBH between all rat groups. It is concluded that 1) HBH preconditioning efficiency does not depend on an innate resistance to SHBH and prior hypoxic experience of rats; and 2) the pretesting to severe hypoxia has no value for predicting the hypoxic preconditioning efficiency and study of adaptive mechanisms.