[Chacterization of human reticulocytes: respiration, Pasteur effect, and electron microscopic findings on mitochondria].

On 5 blood samples of newborns, whose reticulocytes had been enriched by density gradient centrifugation, and on 25 blood samples of different reticulocytoses of man were determined: the extent of intra- and extramitochondrial respiration, coupling of the electron transfer with the oxidative phosphorylation and the electronmicroscopic appearance, and the number of mitochondria. The reticulocytes occurring in the flowing human blood are in general relatively stiff and are characterized by the following properties:--low respiration--low capacity of the respiratory chain enzymes--weakened Pasteur effect --varying proportion of intramitochondrial respiration and total respiration--decoupling of a major part of the intramitochondrial respiration--low number of mitochondria--qualitative changes of mitochondria. However, there are situations of erythropoiesis where immature reticulocytes are discharged in man (similar to the socalled "stress reticulocytes" of rabbits). On the other hand, it could be shown that the reticulocytes of rabbits are mature in the normal state.