Living High-Training Low Improves Erythropoiesis In Rats

Living high-training low (HiLo) is a rising physical training method, which has been applied in an attempt to improve the aerobic capacity of athletes. Some researches have shown that the stimulation of red blood cell production probably is responsible for the improvement of aerobic performance by utilizing HiLo. However, the mechanisms underlying the enhancement of erythropoiesis by HiLo remain to be clarified. There are few extensive researches concerning the effects of HiLo on erythropoiesis. The experimental data are not enough for the relationship between the efficiency of erythropoiesis and the combination of training load with duration of hypoxic exposure in HiLo. The purpose of this work was to make a deep-going investigation on the efficiency of HiLo and its mechanisms of action to enhance erythropoiesis by dynamically examining the changes in erythropoiesis of rats during a 13-day HiLo session.Fifty six SD rats were randomly divided into seven groups (n=8) : 3 groups of HiLo for 3, 6 and 13 days respectively, 3 groups of living low-training low (LoLo) for 3, 6 and 13 days, and 1 group of living low without training. Under the conditions of incremental increase in treadmill-running workload every other day, the training group rats were subjected to an episode of treadmill-running every day. The' rats in living high-training low groups were exposed to hypoxia for six hours after the treadmill-running. Rats were killed immediately after the final hypoxic exposure for the HiLo groups, on the next morning following the final treadmill-running for the LoLogroups, or at the beginning of experimental program for the living low without training group to take the samples of blood and kidneys. Red blood cell (RBC) count, hemoglobin (Hb) content, reticulocyte percentage, erythropoietin (Epo) content and hypoxia-inducible factor-la (HIF-la) protein expression were examined. The following results were obtained.1. The reticulocyte percents of HiLo groups were increased with the increase of training days. Compared with the living low without training group, the reticulocyte percents of groups of 6-day and 13-day HiLo were significantly elevated 0?<0. 05). The reticulocyte percents of LoLo groups were higher than the living low without training group. Compared with the living low without training group, the reticulocyte percents of the group of 13-day LoLo was significantly increased (p<0.05). The reticulocyte percentage of the group of 6-day HiLo was higher significantly than that of the 6-day LoLo group correspondent ly. RBC count and Hb content of the rats in training groups did not change markedly.2. Serum Epo and kidney Epo were increased in all the rats of HiLo and LoLo groups. The Epo content of 6~day and 13-day HiLo groups were significantly increased compared with the living low without training group(/K0. 05), but the difference between 3-day HiLo group and the living low without training group was not statistically significant(p>0. 05). Serum Epo and kidney Epo levels of HiLo groups were increased progressively with the increase in training days. In LoLo groups, the serum Epo was also raised with the increase in training days and up to the highest level on the thirteenth training day. The renal Epo level of LoLo groups reached its maximum on the sixth training day. The renal Epo levels of 6~days and 13-day LoLo groups were significantly higher than that of 3~day LoLo group.Serum and kidney Epo levels of HiLo groups were higher than the corresponding LoLo groups, and the difference between the 13-day HiLo group and the 13-day LoLo group was statistically significant.3. The renal HIF-la protein expression of rats in training groups was significantly increased compared with that of the living low without training group. In HiLo groups, the expression of renal HIF-la protein had an incremental increase with the increase in training days. The differences in expressional levels of renal HIF-la protein were statistically significant among HiLo groups compared with one another (/?<0. 05). The kidney HIF-la protein expression of LoLo groups was up-regulated with the increase in training days. The expressional levels of renal HIF-la protein of 6-day and 13-day LoLo groups were significantly higher than that of for 3-day LoLo group , but there was not a significant difference in the expressional levels between 6-day LoLo group and 13~day one (p>0.05). The renal HIF-la protein expression of the HiLo groups was higher than those of the LoLo groups for the same training days, and the differences in the expressional levels between the 6-day HiLo group and the same days LoLo group was significant, as it was between the 3-day groups.From the present results, it is deduced that living high-training low probably improves the erythropoiesis, and that the possible mechanisms involved in the up-regulated expression of HIF-la and Epo under the conditions of environmental and exercise-induced hypoxia. Although RBC count and Hb content have no significant increase, the younger population in red blood cells probably is larger according to the elevated reticulocyte percentage. This study has provided the experimental evidences for the potentiality of enhancingaerobic performance by HiLo.