Interrelation of Serum Vitamin B 12 , Total Body Vitamin B 12 , Peripheral Blood Morphology and the Nature of Erythropoiesis

Summary. The interrelation of serum vitamin B 12 concentration, body vitamin B 12 , peripheral blood morphology and the nature of erythropoiesis was studied in patients with pernicious anaemia. On presentation the patients were treated with radioactive vitamin B 12 and the retained radioactivity, measured by whole body monitoring, was taken as a measure of the body vitamin B 12 . Post‐treatment results suggest that erythropoiesis became megaloblastic when the serum vitamin B 12 was between 70 and 154 pg/ml and usually when the body vitamin B 12 was between 100 and 660 μg and that the serum vitamin B 12 was of more immediate importance in the nature of erythropoiesis than the body vitamin B 12 . A normal peripheral blood film was no indication of the nature of erythropoiesis but an abnormal film carried a high probability of megaloblastic erythropoiesis. Abnormalities in blood films probably developed after abnormalities in marrow. The correlation found between serum vitamin B 12 and body vitamin B 12 differed from that found in controls and the mean quotient of body vitamin B 12 and serum vitamin B 12 concentration was less than in controls showing that, in the patients studied, there was a disproportionately greater amount of vitamin B 12 in serum compared to controls. The balance of serum vitamin B 12 and body vitamin B 12 may involve at least two mechanisms and folate may have a role in both. One mechanism relates to the release of vitamin B 12 from stores to plasma and the other to the clearance of vitamin B 12 from plasma.