Recombinant human insulin-like growth factor 1 (rh-IGF-1) stimulates erythropoiesis in adult, but not in newborn mice.

The in vivo effect of recombinant human insulin-like growth factor (rh-IGF-1) upon erythropoiesis was studied in inbred BALB/C mice. Unweaned, rapidly growing 20 days old mice and adult female mice received subcutaneous rh-IGF-1 or control injections every 6 h for 48 h. The mice were killed either 12 or 48 h after the last injection, i.e. a study time of 60 and 96 h, respectively. Bone marrow erythroid colony forming units (CFU-E), reticulocytes, haematocrit, serum immunoreactive erythropoietin (siEPO) and body and organ weight were measured. An additional group of young mice were given iron prior to the rh-IGF-1 injections to ensure sufficient available iron. No differences in overall body or organ weights were observed. In the young mice erythropoiesis as measured by bone marrow CFU-E, reticulocytes and haematocrit did not differ between rh-IGF-1 group and controls. When iron alone was given, reticulocytes (P < 0.05) and haematocrit (P < 0.0001) increased significantly, but no further stimulation was seen when rh-IGF-1 injections were given in addition to iron. The adult female mice responded with significantly increased erythropoiesis as judged by increased reticulocyte counts following rh-IGF-1 injections (P < 0.001). No significant effect upon CFU-E and haematocrit was detected. The reticulocyte response was more pronounced at 96 than at 60 h after the first rh-IGF-1 injection. SiEPO was significantly (P < 0.01) lower in the adult 96 h rh-IGF-1 group than in the appropriate control group. In conclusion parenteral iron significantly increased haematocrit in unweaned mice. Short time rh-IGF-1 treatment did not stimulate erythropoiesis in these rapidly growing mice, whether or not iron supplementation had been given.(ABSTRACT TRUNCATED AT 250 WORDS)