The polycythemia of high altitudes: iron metabolism and related aspects.

E RYTHROPOIESIS may be investigated by studying various aspects of iron metabolism in the developing erythrocytes. In such a study, the use of radioactive iron is of great assistance in following the iron from the time it is absorbed through the digestive system until it appears in the hemoglobin of the red blood cells. It is also possible to administer labelled iron intravenously and to study its turnover rate and thus obtain an approximate estimation of the amount which is utilized by the erythropoietic organs in hemoglobin synthesis. An estimation of red blood cell formation in polycythemia of high altitude is of particular interest. It is well known that this type of polycythemia, due to anoxic stimulus brought about by the low atmospheric pressure, is reversible, or in other words, it disappears when the subject returns to a normal barometric pressure environment. It has also been found that there is a very close relationship between the degree of polycythemia and the level of altitude at which the permanent residents live, and that in newcomers the degree of response depends on the severity and the duration of the anoxic stimulus.’ All these factors offer an excellent opportunity for the study of production and destruction of the red blood cells along a physiologic pattern, since in the development of high altitude polycythemia and in the return of the blood values to normal there are no other influences beyond the anoxic one; this probably acts on erythrocytic activity through a hematopoietic factor.24 A study of these problems is presented. This is done chiefly on the basis of iron metabolism, and also by means of studying blood volume, the degree of reticulocytosis and the cytology of the bone marrow, as well as some aspects of hemoglobin pigment catabolism and red blood cell life span. Information has thus been obtained concerning the formation and the destruction of crythrocytes ( erythrokinetics).