The effect of intermittent hypoxic exposure on erythropoietic response and hematological variables in elite athletes

This study aimed to evaluate the changes in the erythropoietin level and hematological variables in wrestlers after intermittent hypoxic exposure (IHE). Twelve wrestlers were assigned into two groups: hypoxia (sports training combined with IHE, n=6) and control (sports training, n=6). An IHE was performed for 10 days, with one day off after 6 days, once a day for about an hour. The concentrations of hydrogen peroxide (H(2)O(2)), nitric oxide (NO), vascular endothelial growth factor (VEGF) and erythropoietin (EPO), as well as total creatine kinase activity (CK) were measured. Also, the hematological markers (Hb -hemoglobin, Ht - hematocrit, RBC - red blood cell, WBC - white blood cell, Ret - reticulocytes) were analyzed. The 6-day IHE caused an increase in the levels of H(2)O(2), NO and VEGF. Similarly, the EPO level and WBC count reached the highest value after 6 days of IHE. The total Ret number increase constantly during 10 days of IHE. The hypoxia group showed a higher CK activity compared to the control. In conclusion, 10-day IHE in combination with wrestling training elevates levels of H(2)O(2), NO and VEGF, and improves the oxygen transport capacity by the release of EPO and Ret in circulation.

Ratio of Creatine Kinase 2 Mass Concentration to Total Creatine Kinase Activity not Altered by Heavy Physical Exercise

Serum creatine kinase isoenzyme 2 concentrations (CK 2 mass) were measured in marathon runners during training and 1 and 2 days after a race and compared with values from 36 acute myocardial infarction (AMI) patients whose total CK and (or) CK 2 activities were similar to those of runners in the basal state. During training, runners had CK and CK 2 activities 53% and 43% above reference values, respectively, and 36% had CK 2 activity > 5% of total CK. Nine runners (26%) showed CK 2 mass values > 6 micrograms/L but < or = 10 micrograms/L; 35 of the AMI subjects, despite having CK activities similar to those of runners, had values > 10 micrograms/L. The ratio of CK 2 mass to total CK activity was significantly (P < 0.0002) different between sexes for runners. At 1 and 2 days after racing, 100% of CK and CK 2 activities and 71% and 57% of the percentages of CK 2 activity, respectively, were abnormally high; 57% and 43% of CK 2 mass values were > 10 micrograms/L, being comparable with those observed for the AMI group. Basal CK 2 mass values of the runners appeared only slightly higher than that for sedentary subjects, but after exercise half the subjects presented increased values similar to those observed for AMI subjects. The ratio of CK 2 mass to total CK activity appeared unaltered by exercise in all but one of the samples assayed, indicating its utility in evaluating CK 2 mass increases originating in skeletal muscle.

Maturational changes in respiratory control through creatine kinase in heart in vivo

The role of creatine kinase in regulation of myocardial respiration was studied in vivo as a function of maturation. Unidirectional creatine kinase flux (JCK), phosphocreatine to gamma-ATP, was measured in newborn lambs (age 3-9 days, n = 8) and mature sheep (age 30-60 days, n = 6) using 31P saturation transfer techniques, and total creatine kinase activity was measured using standard methods. Myocardial oxygen consumption (MVO2) was measured simultaneously via an extracorporeal shunt from the coronary sinus as cardiac work was increased via epinephrine (1-3 micrograms.kg-1.min-1). Findings were as follows: 1) baseline newborn JCK was markedly lower than in mature sheep despite higher levels of MVO2, and this could be related to a decrease in total creatine kinase activity; 2) JCK was substantially higher than the rate of ATP synthesis in both groups at baseline rates of oxygen consumption; and 3) JCK decreased significantly in newborns during increases in MVO2, whereas there was no change in flux rate in the mature sheep during even larger relative changes in work and oxygen consumption. These data imply that creatine kinase does not limit oxidative phosphorylation. However, this enzyme system probably maintains at least an indirect role in respiratory control that is a function of the myocardial developmental state.