Red cell creatine in steady state and stimulated erythropoiesis

Intra- and interindividual variances as well es the age dependency of red cell creatine were studied. Following a single erythropoietic stimulation creatine can stay elevated for many months. A rise of creatine may not only reflect a shift towards a younger cell population but also different erythropoietic sites. The creatine concentration of red blood cells (rbc) has been shown to be an excellent indicator of cell age (1,2,3) and of dynamics of erythropoiesis (3). Intra- and interindividual variances were determined. Fig. 1 (designed according to 4) shows the variance of the method (3)-both for serial determinations and for repeated analyses of the same sample after storing up to 19 days--as well as the variances for the individual person and for a group. It is shown, that the values for one individual are remarkably constant. Fig. 2 illustrates values obtained from presumably healthy persons without evidence of hematological pathology--from newborn to old age. The fat bar represents the values for adults with a mean of 6,64 mg/dl cells and a rather small standard deviation. The mean creatine concentration for very old persons (bar to the utmost right) appears to be higher with a larger standard deviation. However, these values probably should be taken with caution, since some of the persons might have had some minor cardiac or pulmonary difficulty or occult blood loss from the gastrointestinal tract--even though they were declared healthy by the physician of the seniority home. From the age of 6 months on there appears to be no age dependency of rbc creatine concentration.(ABSTRACT TRUNCATED AT 250 WORDS)