RESUMEN
The present experiment was carried out on mice.The changes in contentsof 12 essential trace elements in the brain of mice were measured by inductivelycoupled plasma emission following acute and repetitive exposure to hypoxia.Followingrepeat exposure to hypoxia for one or two runs, the contents of non-soluble in brainhomogenats as was notably decreased,while that of the soluble V was markedly increased,when compared with that of normal group.When the animals were fed for two daysafter four runs of hypoxia,the contents of As,Fe,Cu,Co,Cr,B,and V were all signi-ficantly or very significantly changed in comparison with the normal value.Further stu-dies are needed to find out the biological importance of these changes and the relationshipbetween them and hypoxia tolerance.
RESUMEN
The hypoxia tolerance of mice was significantly increased by repetitive action of auto-hypoxia. The tolerance duration of the 2nd, 3rd, 4th and 5th run was 1.8 2.5 3.0 and 3.6 times longer than that of the Ist one. The survival time of mice that had been exposed to hypoxia repeatedly for four runs was 10 times longer than that of the control animals when both of them were placed in the same low pressure chamber and was 4 times longer while KCN was administrated. The survival time under low oxygen pressure in mice injected with brain extract of resistant mice was 1.8 and 2.1 times longer than that of the saline-injected or normal mice's brain extract-injected animals respectively. These results indicate that some plastic or adaptic changes might occur in the tissue cells particularly in the brain cells during acute and repeated hypoxia. They lead the animals' hypoxia tolerance to a very high level. Water soluble antihypoxic or hypoxia-resistant elements might exist in the brain of hypoxia resistant animals, which were extractable, transferable, and permeable to the blood brain barrier.