Direct effects of thyroid hormones on bone marrow erythroid cells of rats

Abstract

A stimulatory effect on bone marrow cellularity was observed in normal and nephrectomized rats continuously infused with T3 and T4. Results of bone marrow studies are expressed in absolute numbers of total nucleated erythroid cells per milligram of femoral marrow at the beginning and after 8 hr of continuous intravenous infusions. Administration of T3 and T4 to nephrectomized rats produced a marked and significant increase in total erythroid cells counted. After differential analyses of the nucleated erythroid elements, a significant increase in all erythroid cell types was also observed. Similar results were seen in a control group of rats in which both ureters have been previously ligated and in groups of nephrectomized rats receiving rabbit antiserum against erythropoietin before starting the intravenous infusions of T3 and T4. These results indicate that stimulation of marrow erythropoiesis produced by thyroid hormones in our system is not dependent on renal or extra-renal production of erythropoietin. The progressive introduction of T3 and T4 into the circulation of rats with bilateral nephrectomy or ureter-ligated normal rats, may overload the mechanism of transport of these hormones in plasma. As a consequence, a progressive increase in free active forms of T3 and T4 in plasma may occur. Our interpretation of the present findings is that thyroid hormones stimulate directly bone marrow erythropoiesis. This stimulation is clearly evident when high levels of free active forms of thyroid hormones are present in plasma.

Effects of triiodothyronine on the anemia of chronic renal failure

“…The baseline determinations of T3 serum levels were in the range reported by others in patients with similar degree of impairment of renal function [24] and the prescribed dose of T3 was sufficient to produce a suppressive effect on TSH. The doses of T3 used in rats by Malgor et a1 [22] are about 700 times higher, per kilogram of body weight than the doses received by our patients. It is therefore possible that larger doses might induce an erythropoietic effect in man.…”

“…The purpose of the study was to test clinically the direct erythropoietic effect of T3 shown experimentally by Malgor and associates [22] to occur in the absence of erythropoietin. The criteria for selection limited the number of patients available for study but provided a hemogeneous group in which the results could be more easily interpreted.…”

“…111-211. Recently, Malgor and co-workers [22] were able to show in anephric rats that thyroid hormones, particularly triiodothyronine (T3), can induce an erythroid response in the bone marrow not mediated by erythropoietin, while dexamethasone and testosterone required the existence of renal tissue for the same effect. This may account for the poor results obtained with androgenic therapy in anephric patients [21].…”

Control of Hemoglobin Synthesis in Fetal Erythroid Cells by L‐Thyroxine

“…Both in vivo [7] and in vitro [8,9] studies have suggested that thyroid hormone has a direct effect upon erythropoiesis of adult animals. The in vitro studies with canine marrow cells showed that thyroid hormones increased erythroid colony formation, although erythropoietin was a requisite for colony growth.…”

Effect of Hyperthyroidism On Haemopoietic Stem Cell Kinetics In Mice

“…The mechanisms by which TH stimulate the haemopoietic stem cells remain unclear. It was found that the stimulatory effect of TH hormones may be conditioned by a direct influence of TH on cells (Malgor et al, 1975) manifested in facilitating DNA transcription leading to the synthesis of new proteins (Tata, 1963;Tata & Widnell, 1966). A hypothesis was framed (Oppenheimer & Surks, 1975) that the effect of TH on the cells is dependent on the number of 'nuclear binding sites ' (NBS) , 1973).…”