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KMID : 0383119710190010015
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Journal of Aerospace Medicine
1971 Volume.19 No. 1 p.15 ~ p.25
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An Experimental Study on the Relationship between the Duration of Exposure to a Simulated Altitude and the Change in Plasma Erythropoietin in Rats
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문형남/Moon, Hyung Nam
김동성/이종관/최용규/Kim, Dong Sung/Lee, Chong Kwan/Choe, Yong Kyu
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Abstract
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It is widely accepted that there comes a secondary polycythemia following an increased output of circulating erythropoietin in living body should it exposed to a lowered oxygen environment.. On the other hand, it is not quite clear in case of animals being exposed to a lowered oxygen environment when the increased erythropoietin output takes place and how long it is maintained elevated.
Hence, authors have undertaken the present investigation to clarify the relationship between the duration of exposure to a simulated altitude and the corresponding erythropoietin response in the general circulation.
Forty female albino rats ranging in weight from 150 to 200 gm were used as experimental animals which were divided into 7 experimental groups and I ground control group.
Each of experimental groups was exposed 22 hours a day for a varying period of time according
to the group specified, for-.instance, one day for group 1, 2 days for group 2. and so forth until group 7 for 7 days to a simulated altitude of 22,000 ± 2,000ft in a 6 men low pressure chamber. The ground control group was put to the ground until succumbed. The blood was obtained by cardiac puncture from each of the groups at an appropriate time, centrifuged for plasma which was subsequently kept at -15°C for later erythropoietin bioassay. Eighty CF-1 female mice with 15-20 gm in weight were prepared for erythropoietin bioassay in such a manner that the erythropoietin level in the circulating blood of mice could be held lowest. This was achieved by keeping animals at a simulated altitude of 22,000±2,000 ft. for a period of 3 weeks, and then returned to the ground level for full 2 days before receiving 2 intraabdominal injections at an interval of 24hours of 0.5 ml each of stored plasma from each experimental group of rats.
The control bioassay mice were injected intraabdominally the same anount of saline int the same fashion as in experimental bioassay mice. At exactly 24 hours after the last injection, 0.4 μCi of 59Fe citrate was given intraperitoneally for RBC 59Fe incorporation rate determination which was performed 24 hours after the administration. Besides, hemoglobin concentrations, hematocrit ratios and reticulocyte counts were measured as an useful adjunction of evaluating hypoxic response.
The results may be summarized as follows:
1. During exposure to a simulated altitude of 22,000±2,000 ft. for a maximum period of 7´ days, hemoglobin concentrations (gm/) and hematocrit ratios (%) tended to show a gradual increase with the period of stayin at altitude reaching peak value at 7 days-group of 17.5±1.1gm% and 58.9±2.9%, respectively whereas reticulocyte counts began increasing with first day showing peak value in 5 days-group of 9.4±0.7 % with a tendency to decrease thereafter.
2. RBC 59Fe incorporation rates in erythropoietin bioassay mice showed 2 peaks, maximum peak at 2 days-group of 29.3±7.5% and second peak at 6 days-group of 16.2±3.6%. Reticulocyte counts went nearly parallel with changes in RBC 59Fe incorporation rates reaching maximum value at 2 days-group of 5.3±2.1%.
On the basis of the above observations it could be said that an increase in erythropoietin
in rats was induced by an exposure to a simulated altitude of 22,000±2,000 ft. with its peak at the second day of exposure tending to decrease thereafter.
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