Abstract
This study aimed to assess the changes in red blood cell (RBC) energy status and plasma purine metabolites concentration over a one-year training cycle in endurance-trained (EN; n = 11, 20–26 years), and sprint-trained (SP; n = 11, 20–30 years) competitive athletes in comparison to recreationally-trained individuals (RE; n = 11, 20–26 years). Somatic, physiological, and biochemical variables were measured in four training phases differing in exercise load profile: transition, general, specific, and competition. Significantly highest values of RBC adenylate energy charge (AEC; p ≤ 0.001), ATP-to-ADP and ADP-to-AMP ratios (p ≤ 0.05), and plasma levels of adenosine (Ado; p ≤ 0.05) were noted in the competition phase in the EN and SP, but not in the RE group. Significantly lowest plasma levels of adenosine diphosphate (ADP; p ≤ 0.05), adenosine monophosphate (AMP; p ≤ 0.001), inosine (Ino; p ≤ 0.001), and hypoxanthine (Hx; p ≤ 0.001) accompanied by higher erythrocyte hypoxanthine-guanine phosphoribosyltransferase (HGPRT) activity (p ≤ 0.001), were observed in the competition phase in both athletic groups. No significant alterations were found in the erythrocyte concentration of guanine nucleotides in any group. In conclusion, periodized training of competitive athletes’ results in a favorable adaptation of RBC metabolism. The observed changes cover improved RBC energy status (increased AEC and ATP/ADP ratio) and reduced purine loss with more efficient erythrocyte purine pool recovery (increased HGPRT activity and plasma levels of Ado; decreased Hx and Ino concentration).
Highlights
Mammalian erythrocyte (RBC), a unique cell without a nucleus, serves as a model cell in many studies
Significant differences (p ≤ 0.001) between consecutive phases of the annual training cycle were observed in the EN group for weight, body mass index (BMI), and maximal oxygen uptake (VO2max ), while in the SP group for weight, BMI, VO2max, Hct, and lactate (LA) at rest
Knowing that the concentration of adenosine triphosphate (ATP) and adenosine diphosphate (ADP) is always determined by the rate of phosphorylation and dephosphorylation reactions, our results indicate that propelled phosphorylation reactions (ADP to ATP and adenosine monophosphate (AMP) to ADP) are responsible for the increase in adenosine triphosphate/adenosine diphosphate ratio (ATP/ADP) and ADP/AMP ratios and adenylate energy charge (AEC)
Summary
Mammalian erythrocyte (RBC), a unique cell without a nucleus, serves as a model cell in many studies. Apart from its main functions, such as carrying oxygen and carbon dioxide, and controlling the acid-base balance level, erythrocytes exert other roles. They take part in nitric oxide (NO). Metabolism, influence blood rheological properties, and exert the erythrocrine function by releasing vast amounts of ATP and other bioactive molecules [1,2]. All these properties are essential for human response to exercise, especially that of maximal intensity when substantial homeostasis disturbances occur [2,3,4].
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