STUDIES OF PROTOPORPHYRIN: IV. A COMPARISON OF THE ERYTHROCYTE PROTOPORPHYRIN CONCENTRATION WITH THE RETICULOCYTE PERCENTAGE UNDER EXPERIMENTAL AND CLINICAL CONDITIONS 1

Abstract

The presence of protoporphyrin in human erythrocytes was first noted by H. van den Bergh and co-workers (1, 2). Grotepass (3) isolated this porphyrin and identified it as protoporphyrn 9, corresponding to aetioporphyrin III; in other words, the same protoporphyrin as that in the hemoglobin molecule. The significance of the erythrocyte protoporphyrin is not yet clear. Watson and Clarke (4) described evidence in- dicating that much of it is contained in the reticulocytes. This was likewise the conclusion of de Langen and Grotepass (5). In Watson and Clarke's study (4), it was shown that upon centrifuging various samples of blood, the protoporphyrin was regularly found in the upper, or reticulocyte-rich, strata. It was also observed that samples of red cells composed entirely of reticulocytes, as obtained from rabbits with acute phenylhydrazine poisoning, were especially rich in protoporphyrin. At that time, a satisfactory method for quantitative determination of the erythrocyte protoporphyrin was not available and consequently, the question of correlation of the amount of porphyrin with the reticulocyte per- centage, in various clinical and experimental con- ditions, could not be investigated. In a series of papers appearing between 1933 and 1940, Seggel and others (6 to 10) described evidence indicat- ing that the erythrocyte protoporphyrin resides in "fluorescytes," i.e., red blood cells exhibiting red fluorescence in ultraviolet light. Simultane- ous reticulocyte and fluorescyte curves, as ob- tained in Seggel's studies, were not parallel. Thus, in cases of pernicious anemia which were followed through the reticulocyte response to liver extract therapy, the fluorescytes increased