The association of the urobilin "early peak" and erythropoiesis in man.

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Abstract
An "early peak" of labeled fecal urobilin excretion occurs during the first few days after the intravenous administration of glycine-2-Cl4 to man. To determine if this early peak is associated with erythropoiesis 4 patients with hematologic diseases and 2 hematologically normal patients were given glycine-2-Cl4 a precursor of bile pigment, and thereafter determinations were made of the amount of radio-activity in the fecal urobilin. Three patients were studied when erythropoiesis was virtually absent, and in all 3 instances the specific activity of the fecal urobilin-C14 was markedly reduced when compared to hematologically normal subjects. Two patients were studied a 2nd time during a period of reticulocytosis and rising hemoglobin concentration. The maximal specific activity in urobilin-Cl4 increased approximately 10-fold in 1 patient and 60-fold in another. Thus, the maximal urobilin-C14 specific activity was shown to be low initially when compared with normal and to increase markedly when erythropoiesis was active. This suggests that a small early labeled peak is present in man in the absence of erythropoiesis but that the bulk of the peak is associated with red cell formation in the marrow of these patients. A 4th patient with anemia and normoblastic hyperplasia of the marrow was studied 4 times. In this patient the maximal urobilin-C14 specific activity was shown to decrease by approximately 13-fold concomitant with return of the bone marrow toward normal and return of effective erythropoiesis.