VERY LOW-DENSITY LIPOPROTEIN HEMATOPOIESIS INHIBITOR FROM RAT PLASMA

  • 1 January 1980
    • journal article
    • research article
    • Vol. 8  (7) , 895-905
Abstract
Although the stimulatory effect of specific glycoproteins on bone marrow cell proliferation is acknowledged, little attention had been directed toward growth inhibitors. In this report the role of plasma lipoproteins in regulating the proliferation of hematopoietic cells was explored. Lipoproteins were isolated from the plasma of normal rats and rats with cancer by density gradient ultracentrifugation. Lipoprotein fractions were then added to cell cultures to assess their effect on the following: erythropoietin (Ep) stimulated rat marrow DNA and protein synthesis; Ep and colony stimulating factor induced marrow colony formation (CFUE [erythroid colony forming units], CFUC [granulocytic progenitor cells]); and phytohemagglutinin (PHA) stimulated lymphocyte DNA synthesis. Very low density lipoproteins (VLDL) apparently completely inhibited CFUE and CFUC formation. VLDL inhibited (> 80%) the synthesis of DNA by marrow cells cultured with Ep and lymphocytes cultured with PHA. VLDL from rats with Walker-256 cancer had a greater inhibitory effect than normal rat VLDL. Chylomicrons had a moderate growth inhibitory effect, and plasma LDL [low density lipoprotein] and HDL [high density lipoprotein] were inactive. VLDL did not inhibit the proliferation of rat fibroblasts. Physiologic concentrations of plasma VLDL have a significant inhibitory effect on the proliferation of erythroid, granulocytic and lymphocytic cells. A pathophysiologic role for VLDL in the impairment of erythropoiesis and immune function in cancer is suggested.