Action of Growth Hormone on Erythropoiesis: Changes in Red Blood Cell Enzyme Activities in Growth-retarded Patients with and without Growth Hormone Deficiency

摘要

Extract: Fifteen red cell enzyme activities of growth-retarded patients with and without growth hormone (GH) deficiency were investigated before and after GH administration. The 15 enzymes were Hexokinase, phosphoglucomutase, glucose phosphate isomerase, phosphofructokinase, fructose diphosphate aldolase, glyceraldehyde-3-phosphate dehydrogenase, triosephosphate isomerase, 2,3-diphosphoglycerate mutase, 3-phosphoglycerate kinase, 3-phosphoglycerate mutase, enolase, pyruvate kinase, glycose-6-phosphate dehydrogenase, 6-phosphogluconic dehydrogenase, glutathione reductase.Sixty-six subjects were studied: 30 normal control subjects (group N) and 36 patients (aged 5–23 years) with short stature. Complete endocrine evaluation showed 21 (group I) to have GH deficiency (10 patients with isolated GH deficiency) and 15 (group II) to have normal hypothalamic and pituitary function except for two patients with a moderate hypothyroidism. Both had been receiving thyroid hormone treatment for a long time before our studies. All 36 patients were treated with 2 mg human growth hormone intramuscularly for 7 days.Before GH treatment no significant difference was observed between hematologic data in group I (GH deficiency) and group II (no GH deficiency). After GH therapy there was a significant increase in reticulocyte count in both groups of patients with short stature. The mean pretreatment value in group I was 1.294% ± 0.084 (SEM); the mean post-treatment value was 2.081% ± 0.287 (SEM), P group II was 1.0% 0.184 (SEM); the mean post-treatment value was 1.407% ± 0.193(SEM), P group II (no GH devidiency) mean pretreatment erythrocyte enzyme activities were not significantly different from those activities observed in normal control subjects (group N). However, in patients who lacked GH, the pretreatment activities of five red cell enzymes (glucose phosphate isomerase, triosephosphate isomerase, glyceraldehyde-3-phosphate dehydrogenase, 2,3-diphosphoglycerate mutase, 3-phosphoglycerate kinase) were significantly decreased before GH administration compared with the values in normal control subjects. The reduction in a further red cell enzyme (3-phosphoglycerate mutase) was statistically not significant.With GH treatment eight red cell enzyme activities showed a significant increase, one of them (hexokinase) significantly rising in both groups of patients. The remaining seven erythrocyte enzymes (3-phosphoglycerate mutase, glucose phosphate isomerase, triosephosphate isomerase, 2,3-diphosphoglycerate mutase, enolase, pyruvate kinase, glucose-6-phosphate dehydrogenase) exhibited significantly elevated activities only in patients lacking GH. In three of these enzymes the increase was significantly above the control value.Enzyme activities which were significantly decreased before GH administration rose significantly after GH therapy except for two enzyme activities (3-phosphoglycerate kinase and glyceraldehyde-3-phosphate dehydrogenase). The data may suggest the presence of a younger red cell population after GH administration.Speculation: The increase in red cell enzyme activities after GH treatment is supposedly due to stimulation of erythropoiesis by growth hormone. An additional stimulatory effect of GH on nucleated red cell enzyme synthesis is less likely but cannot be definitively excluded.