Studies on the Hemolytic Nature of Protein-deficiency Anemia in the Rat.

ATS subjected to total protein deprivation ( PD ) over a period of 7 to 10 weeks develop severe hematologic disturbances such as leukopenia and hypochromic microcytic anemia. The characteristics of this syndrome, observed as early as 1937 by Orten et al.,53 have since been described in detail by both Orten52 and Aschkenasy and his colleagues.1’3’12’20 The anemia an(l leukopna, due in part to an exhaustion of tissue reserves of amino acids essential to hemopoiesis and erythroid metabolism, is potentiated l)y a decrease in the level of certain hemopoietically active vitamins2’12”9’2#{176} as well as by endocrine disturbances such as thyroid and gonad hypoactivity and relative adrenal hyperactivity.4’#{176}8’ 3 Two possible mechanisms have been suggested for the anemia of experimental PD : ( 1 ) intramedullary inhibition of red cell maturation and/or release into the peripheral circulation; and ( 2 ) intravascular hemolysis of intraor extracellular origin. The hypothesis of an intramedullary block causing PD anemia is supported by the findings of ( 1 ) significant peripheral reticulocytosis during the first days of protein refeeding following PD’2 and (2) an intramedullary maturation arrest at the erythroblast and reticulocyte50’51 stages. Such an arrest, noticed especially during the first two weeks of PD,1’#{176}11 appears much less pronounced after more prolonged protein deficiency when, even prior to protein refeeding, an increase in peripheral reticulocyte levels is observed. Erythrocyte Fe59 uptake shows the same pattern as peripheral reticulocyte numbers: a marked decrease during the first weeks, followed by a considerable increase during the late stages of PD.11 The paradoxic increase in bone marrow erythropoietic activity following protracted PD, paralleling a pronounced anemia, appears to be explained most readily by an increase in peripheral hemolysis-a hypothesis further substantiated by the observation of splenic siderosis in PD rats.1’5 To test this hypothesis, we investigated the in vitro response to known hemolytic agents and the in vivo survival of PD erythrocytes. Our preiminary results17’18 indicated that a structural defect in these erythrocytes is not in itself sufficient to account for the severity of intravascular hemolysis. Abnormal serum protein and lipid fraction concentrations were observed in the PD rat,33 a condition confirmed by more detailed studies of one of us (Aschkenasy’5) and Weimer et al. #{176}Consequently, we investigated the effects on the in vitro hemolytic behavior of PD erythrocytes of both whole serum and those serum fractions (albumin, cholesterol, lecithin) whose concentrations are most severely reduced in PD.