The maturation rate of reticulocytes.

By MARIO BALDINI AND Ivo PANNACCIULU T HE RED BLOOD CELLS, after release from the bone marrow, continue their “maturation” in the peripheral blood. Here, the immature red cells, the reticubocytes, become mature erythrocytes. The time necessary for the reticulum substance to disappear has been defined as the “maturation time” of reticulocytes. In the past, the maturation time of reticubocytcs has been studied by in vivo and by in vitro technics. In vivo studies were performed in pernicious anemia patients during reticubocyte “crisis” ’ or in animals treated with phenylhydrazine.4 Other experiments were done transfusing normal blood into aplastic subjects.57 The main limitations of all these experiments were that they could only be performed in abnormal and often unstable conditions, and that, in humans, they could not be repeated in series. Studies in vitro were done by Nizet, Seip, and others.#{176}’8” 3’19’2’ It has been demonstrated on numerous occasions that reticulocytes in vitro are transformed into mature red cells by an aerobic fermentative proccss. 3 The in vitro requirements of the cells are not the same as those in vivo, although in vitro the environment remains substantially unmodified during the experiment, and the effect of variables can be excluded. Furthermore, experiments in vitro can be reproduced ad libitum with controlled conditions which are indispensable for a systematic comparative study. In vitro studies, therefore, present many advantages. The first part of the present investigation was concerned with the establishment of a technic and the demonstration of its validity. The maturation time of reticulocytes was then studied in different types of anemias. \Vith increased red cell regeneration, the number of reticiilocytes in the circulating blood becomes increased, and younger forms with greater amounts of reticulum substance also appear. Obviously, the presence of younger reticulocytes causes an increase in the maturation time of these cells. The question, however, of whether in some conditions the maturation time of reticubocytes can also be increased because of a “delayed” rate of maturation, due to a metabolic defect of these cells, has never been clearly defined. This problem has been investigated in the present study, and the findings are of special interest with reference to the pathophysiology of erythropoiesis in anemias.