Influence of growth rate on the ability of hypertransfusion induced plethora to suppress erythropoiesis in the growing rat.

To induce different rates of growth male rats 23 days of age were places on diets containing no protein or 20% casein for 10 days. They were then divided into three subgroups which were placed on diets containing 5%, 10% or 20% casein until the end of the experimental period (day 17). Adult rats were used as controls. Rats were hypertransfused on days 8 and 9 and RBC-59Fe uptake determined on day 17. Body weight was directly correlated with the casein content of the diet in the growing rats. RBC-radioiron incorporation was also influenced by the protein content of the diet in the young rats in spite of the fact that hematocrits were over 60% in all the animals. On the contrary, 59Fe uptake by erythrocytes was not related to diet composition in the adult rats. When radioiron incorporation values were plotted against growth rate it became evident that a close direct correlation exists between erythropoiesis and growth rate in transfused-polycythemic rats, indicating that the degree of suppression of red cell production provoked by hypertransfusion-induced plethora is dependent on the rate of growth of the animal, keeping with it an inverse relationship.