620 XIII. HEMOGLOBIN AND PORPHYRIN SYNTHESIS 



iron of the blood. Copp and Greenberg {J^89) showed, however, in 

 experiments with radioactive iron that cobalt accelerates the rate of 

 hemoglobin formation in the bone marrow and mobilizes liver iron.* 



Other substances. The need of other trace metals for hemopoiesis or 

 cytopoiesis has been claimed repeatedly, but there is little certain evidence. 

 A small amount of manganese appears to be necessary for hemopoiesis in 

 rats. This was first claimed by Titus and Cave {2806) ; while at first in doubt, 

 it has more recently been confirmed {2571,2900). Arsenic, given in addition 

 to manganese, is claimed to increase hemopoiesis still further {2571). A 

 high calcium diet depresses hemoglobin formation {53,959,1547,2542), 

 probably by interfering with iron absorption. On the other hand, Day and 

 Stein {545, cf. also 53,2542) observed mild anemia (and polycythemia) 

 caused by an excess of phosphorus over calcium. An extreme salt restriction 

 increases the erythrocyte count but decreases hemoglobin formation; there 

 is no evidence of increased ^breakdown of hemoglobin (Orten and Smith, 

 2089). 



3.4. Control of Hemopoiesis by Endocrine Factors 



According to Wintrobe {3103) a clear-cut relationship of endocrine factors 

 to the development of anemia in man remains to be established. While 

 there are some observations on the effect of hormones on hemopoiesis, there 

 is no evidence that they act directly upon hemoglobin synthesis. The subject 

 has been reviewed by Querido {2195). 



Thyroxine and thyroid have been claimed to increase hemopoiesis. No 

 immediate effect of thyroidectomy is, however, noticeable. f Wintrobe {3103) 

 assumed that in some cases of myxedema the anemia may be caused by 

 achlorhydria and lack of antipernicious anemia principle but the anemia is 

 not benefited by the administration of liver extract {118). Thyroxine has 

 been found to increase the blood copper level {2009). 



Hypophysectomy causes anemia {1930,2395). Flaks and co-workers {905) 

 observed reticulocytosis after feeding pituitary gland to rats, and assume 

 the existence of a hemopoietic hormone in the pituitary. After hypophysec- 

 tomy the stimulus of anoxia {cf. below) was found to be no longer effective 

 in increasing hemopoiesis {1030). Anemia is found in pituitary hypoplasia — 

 polycythemia and erythremia in diseases with pituitary hypertrophy (r/. 5^^?). 

 Witts and co-workers {2586) assume that the cause of the anemia may be 

 achlorhydria. Prolan stimulates hemopoiesis {1574), while injections of large 

 doses of pituitrin depress it {1003,1816). 



Androgens stimulate hemopoiesis while estrogens depress it {762,1805, 

 2463,2619,2729). Insulin causes only a passing decrease, but animals chroni- 

 cally treated with insulin develop hyperplasia of the bone marrow {1658). 

 Vagotonin has been found to increase hemopoiesis {1029). Adrenaline pro- 

 duces an increase of hemoglobin and erythrocyte number mainly by causing 



* Cf. also \Vintrol)e and co-workers {■ilOoa). 



t Gordon and co-workers {1024b) found, however, hemoglobin synthesis after bleed- 

 ing inhibited by thyroidectomy. 



