Induced synthesis of albumin-like protein in damaged rat reticulocytes

Abstract We have used succinylacetone (4,6-dioxoheptanoic acid), a specific inhibitor of delta-aminolevulinic acid dehydrase, to gain insight into the defect in iron metabolism in the Belgrade anemia. The Belgrade rat has an inherited microcytic, hypochromic anemia associated with poor iron uptake into developing erythroid cells. Succinylacetone inhibits heme synthesis, leading to nonheme iron accumulation in mitochondria and cytosol of normal reticulocytes. When succinylacetone is used to inhibit Belgrade heme synthesis, iron from diferric transferrin does not accumulate in the stromal fraction that contains mitochondria, nor does 59Fe accumulate in the nonheme cytosolic fraction. Hence, the defect in the Belgrade rat reticulocyte occurs in the endocytic vesicle or in a step subsequent to iron transit from the vesicle but before the nonheme cytosolic or mitochondrial iron fractions. Therefore, the mutation affects either the release of iron from transferrin or iron transport from the vesicle to the mitochondrion.

Download Full-text

Der Ribonucleinsäure-Stoffwechsel in Erythrocyten

Zeitschrift für Naturforschung B ◽

10.1515/znb-1964-0311 ◽

1964 ◽

Vol 19 (3) ◽

pp. 248-255 ◽

Cited By ~ 3

Author(s):

Hans-Georg Schweiger ◽

Eva Schweiger ◽

Ingeborg Vollertsen

Keyword(s):

Uric Acid ◽

Phosphate Buffer ◽

Rna Degradation ◽

High Rate ◽

Rat Reticulocytes

During a seven hours period of incubation in vitro rat reticulocytes lose about half of their RNA. This degradation, which proceeds at an especially high rate during incubation in isotonic phosphate buffer, is stimulated by glucose.The greater part of the RNA degradation is due to the ribosome fraction. Apparently the degradation of the ribosomes to acid soluble products is preceded by a breakage to acid-insoluble slowly sedimenting compounds. The following acid-soluble products have been identificed: cytidine, uracil, 2′,3′-GMP, uridine, 2′,3′-CMP, adenine, 2′,3′-UMP, cytosine and uric acid.

Download Full-text

Biphasic uptake of iron-transferrin complex by L1210 murine leukemia cells and rat reticulocytes

Biochimica et Biophysica Acta (BBA) - Biomembranes ◽

10.1016/0005-2736(82)90027-x ◽

1982 ◽

Vol 685 (1) ◽

pp. 6-12 ◽

Cited By ~ 23

Author(s):

Kiyoshi Takahashi ◽

Mehdi Tavassoli

Keyword(s):

Leukemia Cells ◽

Rat Reticulocytes ◽

Murine Leukemia

Download Full-text

Receptor-mediated endocytosis of transferrin and recycling of the transferrin receptor in rat reticulocytes.

The Journal of Cell Biology ◽

10.1083/jcb.97.2.329 ◽

1983 ◽

Vol 97 (2) ◽

pp. 329-339 ◽

Cited By ~ 819

Author(s):

C Harding ◽

J Heuser ◽

P Stahl

Keyword(s):

Plasma Membrane ◽

Transferrin Receptor ◽

Intracellular Membrane ◽

Coated Pits ◽

Surface Receptors ◽

Receptor Mediated Endocytosis ◽

Freeze Dried ◽

Inner Surface ◽

Multivesicular Endosomes ◽

Rat Reticulocytes

At 4 degrees C transferrin bound to receptors on the reticulocyte plasma membrane, and at 37 degrees C receptor-mediated endocytosis of transferrin occurred. Uptake at 37 degrees C exceeded binding at 4 degrees C by 2.5-fold and saturated after 20-30 min. During uptake at 37 degrees C, bound transferrin was internalized into a trypsin-resistant space. Trypsinization at 4 degrees C destroyed surface receptors, but with subsequent incubation at 37 degrees C, surface receptors rapidly appeared (albeit in reduced numbers), and uptake occurred at a decreased level. After endocytosis, transferrin was released, apparently intact, into the extracellular space. At 37 degrees C colloidal gold-transferrin (AuTf) clustered in coated pits and then appeared inside various intracellular membrane-bounded compartments. Small vesicles and tubules were labeled after short (5-10 min) incubations at 37 degrees C. Larger multivesicular endosomes became heavily labeled after longer (20-35 min) incubations. Multivesicular endosomes apparently fused with the plasma membrane and released their contents by exocytosis. None of these organelles appeared to be lysosomal in nature, and 98% of intracellular AuTf was localized in acid phosphatase-negative compartments. AuTf, like transferrin, was released with subsequent incubation at 37 degrees C. Freeze-dried and freeze-fractured reticulocytes confirmed the distribution of AuTf in reticulocytes and revealed the presence of clathrin-coated patches amidst the spectrin coating the inner surface of the plasma membrane. These data suggest that transferrin is internalized via coated pits and vesicles and demonstrate that transferrin and its receptor are recycled back to the plasma membrane after endocytosis.

Download Full-text