Emin Kansu

Renal and Extrarenal Erythropoietin Production in Anaemic Rats

Summary. Rats were rendered anaemic by a single bleeding or by a single injection of phenylhydrazine. At various times after the onset of anaemia they were nephrec‐tomized and challenged with a 6 h exposure to hypoxia. The erythropoietin titre observed at the end of this hypoxic period was corrected for renal erythropoietin induced by the anaemia alone, and the resulting extrarenal component was compared to total erythropoietin production of nephric rats in response to anaemia plus 6 h hypoxia. Extrarenal erythropoietin production was found to increase from 10.3% in normal rats to 12.5% in moderately anaemic rats to 15.1% in rats with severe bleeding anaemia. In phenylhydrazine‐treated rats this extrarenal component was found to be 18.3% possibly due to stimulation of extrarenal erythropoietin by haemolysed red cells. Chronic phenylhydrazine administration resulted in splenomegaly and Kupffer cell hyperactivity but not in any further stimulation of extrarenal erythropoietin production.

Plasma erythropoietin in polycythemia

Erythropoietin titers of plasma cannot be used to differentiate polycythemia vera from secondary polycythemia since the limit of sensitivity of our current bioassay technics is 50 mU, considerably higher than levels found in normal subjects and in patients with polycythemia. However, erythropoietin is relatively heat stable, and since abundant plasma is available from therapeutic phlebotomies it is possible to prepare and assay highly concentrated, erythropoietin-containing extracts. In 35 normal subjects, erythropoietin levels ranged from less than 5 mU/ml (the limit of sensitivity) to 18 mU/ml with a mean of 7.8 mU/ml. In 21 patients with proved polycythemia vera, the levels were less than 5 mU/ml in all. In 41 patients with suspected secondary polycythemia or polycythemia of unknown origin, the levels ranged from less than 5 to 3,000 mU/ml. Three of the 11 patients with levels less than 5mU/ml were subsequently shown to have polycythemia vera. These results suggest that this refinement of the routine bioassay for erythropoietin may be of clinical importance in the differential diagnosis of polycythemia.

Suppressor cell population in Sézary syndrome

Abstract In the present study, T lymphocytes from a patient with the Sezary syndrome were shown to suppress the synthesis of immunoglobulin in B lymphocytes. Immunoglobulin synthesis and secretion were measured in cultures containing lymphocytes and pokeweed mitogen. Although normal peripheral blood lymphocytes synthesized immunoglobulin in vitro, lymphocytes from the Sezary patient were incapable of immunoglobulin synthesis. After fractionation of normal and Sezary lymphocytes into T- and B-cell populations, immunoglobulin synthesis was demonstrated in cultures containing normal T and Sezary B cells, but not in cultures of Sezary T and normal B cells. When Sezary T lymphocytes were cocultured with both normal T and B cells, immunoglobulin synthesis was suppressed by 80%, compared to appropriate controls. These studies demonstrate that malignant transformation of T lymphocytes in the Sezary syndrome can result in the generation of cells which suppress immunoglobulin synthesis. Furthermore, B cells from this patient were capable of synthesizing immunoglobulin, predominantly IgA, in the presence of normal T cells.

Spectrin loss during in vitro red cell lysis

Spectrin was extracted from washed erythrocyte ghosts in 1 mM EDTA buffer (pH 8.0) and purified to homogeneity by gel filtration. Anti-human spectrin was raised in rabbits. Specificity of the antibody was demonstrated by immunodiffusion, immunoelectrophoresis and immunofluorescent techniques. Membrane-free hemolysate prepared by lysing red cells in 5 mM phosphate buffer (pH 8.0) for variable intervals (5--60 min) at 4 degrees C was found to contain spectrin identifiable by immunodiffusion, immunoelectrophoresis, immunofluorescence and sodium dodecyl sulfate polyacrylamide gel electrophoresis. Spectrin was demonstrable in ultracentrifuged membrane-free hemolysate and, in progressively decreasing amounts, in membrane washes. Membrane-free hemolysate contained more spectrin when erythrocytes were lysed for 60 min than for 5 min. The data indicate that a significant amount of spectrin is detached from the membrane following sysis in hypotonic buffer for different time intervals. Spectrin lost in this manner might be part of spectrin attached to the lipid bilayer.