Effects of Growth Hormone on Erythropoiesis in the Intact Rabbit and the Polycythemic Mouse

Abstract Electrical stimulation of the hypothalamic region may produce reticulocytosis and increased red cell mass in intact rabbits (Seip et al. 1961). In order to compare the effect of hypothalamic stimulation on erythropoiesis with the effect of growth hormone (GH), daily GH injections have been given to intact rabbits, and the changes in erythropoiesis have been followed with the same parameters as in the previous study. GH caused a marked peripheral reticulocytosis which was very similar to that following hypothlamic stimulation, and the slope of both curves was similar to those following hypoxia or erythropoietin injections. GH did not, however, cause an increase in ROM. Hemoglobin, erythrocytes and hematocrit decreased, especially during the first days of GH administration, mainly due to hemodilution. The red cell size increased following GH treatment. The plasma erythropoietin levels in the GH treated rabbits were not significantly increased. These findings confirm and extend previous findings of the effect of GH on erythropoiesis, and indicate that the effects of hypothalamic stimulation cannot be explained on the basis of increased GH production alone. The effect of GH on erythropoiesis in the polycythemic mouse was also studied. The results indicate that there is no effect on the stem cell level. Porcine growth hormone did not increase Fe59 uptake into red blood cells in polycythemic mice when given alone or when given in addition to standard erythropoietin. The reticulocyte response to a single dose of standard erythropoietin changed slightly when growth hormone was added.