Creatine and Phosphocreatine in the Human Red Cell

Abstract

In vitro experiments showed that the concentration of creatine in a mixed population of normal red cells was either unchanged or slightly diminished during incubation at 37° C. for 48 hours in plasma or a buffered medium. If young cells were present there was always a fall in creatine during the early stages of incubation. Creatine lost in this way appeared in the cell‐free supernatant fluid. The ability of the red cell to retain some creatine throughout its life span is due to the relative impermeability of the cell membrane to this substance. Traces of phosphocreatine and creatine phosphokinase were detected in a population of young cells but not in mature cells. It is unlikely, therefore, that creatine takes part in energy transformations in the non‐nucleated red cell, although it may do so in an earlier phase of its development. The origin of the red‐cell creatine is obscure. Synthesis of creatine by young, non‐nucleated, red cells was not detected in vitro and its derivation from plasma creatine is considered unlikely because of the impermeability of the cell membrane. It is suggested that the creatine is acquired by the cell at some stage in its development from nucleated precursors.

Myocardial density and composition: a basis for calculating intracellular metabolite concentrations

“…The concentration of ATP in RBC is 2 mM (28), in cytoplasm it is 16 nmol/mg cell protein, and in the mitochondria it is 4 nmol/mg cell protein (16), which translate into the molar concentrations of Table 6. There is no PCr in normal RBC (18). The rat heart PCr concentration is 39.4 mol/g dry weight (31), giving 20.8 mM in cytoplasmic water space.…”

Analysis of creatine, creatinine, creatine-d3 and creatinine-d3 in urine, plasma, and red blood cells by HPLC and GC–MS to follow the fate of ingested creatine-d3

“…creatine after 5 days of supplementation [25], while no change was reported in the first few hours after ingestion of a 5 g dose [26,27]. The creatine-d 3 presumably entered because of slow exchange with creatine in the plasma.…”

Hereditary Leaky Red Cell Syndrome in a Swiss Family

“…The creatine content of red cells is an accepted sen sitive criterion of the mean age of an erythrocyte pop ulation, and the correlation between the number of circulating reticulocytes and the mean creatine con tent of red cells is excellent [13,27], It was, therefore, surprising to find normal or only slightly increased creatine values in the patients with clearly elevated reticulocyte counts (table I). In the first 24-48 h of storage, creatine loss from red cells is small, even in blood containing many young creatine-rich reticulo cytes [27], In vitro losses could not account for our low values as assays were done within less than 24 h after sampling. Creatine measured in red cell sedi ments can be erroneously low, because aspiration of the buffy coat might inadvertently remove a reticulocyte-rich layer, leaving older cells behind for analysis.…”