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The erythrocyte ferritin content was measured in 183 healthy subjects in age from 4 to 68 years; 80 were male and 103 were female. In children between the ages of 4 and 12 years there is no significant difference in the mean value between boys and girls. In females the erythrocyte ferritin concentration is independent of age. After 12 years of age the erythrocyte ferritin content is higher in men. Reference intervals were determined by the two quantiles 0.05 and 0.95. The reference interval is 3-24 age by cell in boys between 4 and 12 and females between 4 and 63; the reference interval is 5-38 age by cell in males between 13 and 68 years of age.

Erythrocyte histograms should be analysed in accordance with the ICSH recommended protocol to determine: How many red cell populations are present and the proportion of the total red cells which are included in each population. The central tendency (mode, median & mean) and dispersion (size ratio, geometric standard deviation & coefficient of variation) for each population. The proportion of microcytic or macrocytic cells in each population. Examples are given to show how the patient's diagnosis is assisted by careful analysis of the histograms and the effect of treatment monitored by sequential testing. Histograms can be generated from blood films or from aperture-impedance and light-scatter volume measurements. Volume measurements on these systems are influenced by the red cell shape and internal refractive index. Mean cell hemoglobin concentration affects both shape in the aperture-impedance orifice and internal refractive index in light-scatter systems. There is poor agreement between volume histograms obtained on the two measuring systems and the histograms available on current automated instruments provide no more useful information than can be obtained from the blood film. Automated instruments need to produce histograms with fewer artefacts and the histograms should then be examined in accordance with the ICSH protocol. This approach should maximise the diagnostic value of the complete blood count.

1. Transferrin-membrane complexes and iron-binding membrane complexes were solubilized with sodium dodecyl sulfate from the plasma membranes of reticulocytes that had been incubated with (59Fe,125I)-labeled transferrin. Gel filtration of solubilized material demonstrated 125I-labeled transferrin complexed to two moieties, a minor component (Peak I) of apparent molecular weight 435,000 and a major component (Peak II) of apparent molecular weight 200,000. Most of the membrane 59Fe was located in Peak I. 2. Sepharose-bound anti-transferrin was used to purify the 125I-labeled transferrin-membrane complexes. The 59Fe/125I ratio in the transferrin complex purified from Peak I was the same as in the original transferrin and thus contained membrane-bound transferrin to which the 59Fe was still attached. The 59Fe/125I ratio in the purified Peak II transferrin complex was 0.33 times that of the original transferrin, indicating that more than 60% of its 59Fe had been delivered to the reticulocyte. 3. The purified transferrin complexes analyzed by SDS-polyacrylamide gel electrophoresis demonstrated a single band of apparent molecular weight 78,000 both by Coomassie blue stain for protein and by 125I radioactivity. The specific activity of this material was 0.27 and 0.56 times that of the original transferrin for Peak I and Peak II, respectively, indicating that transferrin in Peak I and II was bound to a membrane component with a molecular weight similar to that of transferrin. 4. The isoelectric focusing pattern of the Peak II transferrin complex showed isoelectric points of pH 6.7 and 6.2 compared to pH 5.4 for transferrin. 5. On the basis of these studies we propose that transferrin is first bound to a membrane protein and then delivers iron to a membrane component distinct and separate from the transferrin-binding moiety. Prior to its release, transferrin markedly depleted of iron is still bound to a component in the plasma membrane.

1. Compounds which are believed to cause derangement of the structural components of the plasma membrane and of microtubular function were preincubated with reticulocytes to study their effects on transferrin and iron uptake by the stroma and cytosol fractions of the cell. 2. Proteolytic enzymes, chelating agents (EDTA, EGTA), neuraminidase, concanavalin A and primaquine all inhibited iron binding in the cytosol fraction. Thus, their mode of action may be on the cell membrane, probably resulting in a loss of transferrin receptors or a reduced ability for the protein to interact with the receptor. 3. Pharmacologic agents known to interfere with endocytotic activity of the cell produced both inhibitory and stimulating effects on iron building by the cell. Nicotine reduced iron binding in the stroma and cytosol while colchicine and hydrocortisone enhanced cytosol-bound iron. 4. The inhibitory action of metabolic inhibitors on iron uptake by reticulocytes was accompanied by an accumulation of transferrin and ion in the stroma suggesting that a block in the iron release from transferrin occurs at the stroma level. As the stroma included some mitochondria, the possibility that such blockage may occur in these organelles cannot be ruled out entirely.

The results of the electrophoretic phenotyping of two serum groups (C'3 and Transferrine) and seven red cell enzymes (PAc, PGM, AK, ADA, 6PGD, sGPT and Est D) in two groups of negroes from Gabon are presented. The frequencies are in the normal range observed for African populations except for acid phosphatase in Southern Africa; Khoisan people have frequencies of the "Negroe allele R" higher than in any other population of the world. In Obamba and Bateke populations frequencies of Pr is 0.013.

A number of haematological parameters were monitored in eight-month-old Merino wethers, six infected with 10,000 Haemonchus contortus and 13 controls. Blood loss caused by infection was reflected in a decrease in packed cell volume (r = -0.78; P less than 0.001), and was correlated with faecal egg excretion (r = 0.89; P less than 0.001). Infected animals showed a decline of serum iron content and increased serum transferrin levels. Erythrocyte potassium concentration showed a high correlation with erythropoiesis as measured by iron59 clearance from blood (r = 0.79; P less than 0.001). As potassium assays are quick, inexpensive and samples can be stored for long periods, this parameter seems particularly useful in large experiments.

Erythrocyte protoporphyrin (EP) was measured in 50 normal control subjects, 22 iron-responsive anemic subjects, and in 106 patients with thalassemic diseases. All normal subjects had EP of less than 80 micrograms/dL red blood cells, whereas all iron-deficiency subjects had EP of more than 80 micrograms/dL red blood cells. Six of 22 heterozygotes for thalassemias had elevated EP, and all of these had transferrin iron saturation of less than 16%, reflecting a complicating iron deficiency. Among 52 patients with beta-thalassemia/hemoglobin (Hb) E disease, 26.9% had elevated EP levels, and among 32 patients with Hb H disease, 40.6% had elevated EP. These elevated EP levels were associated with transferrin iron saturation between 18 and 44%. In none of the thalassemic patients with transferrin iron saturation above 44% was EP elevated. These findings suggest that elevation of EP in some thalassemic patients causally is related to iron supply inadequate for the massively expanded erythropoiesis. This relative iron deficiency in thalassemia occurs at a transferrin iron saturation level usually considered to be normal. These relationships demonstrate the need for an increased iron supply in patients with erythroid marrow hyperplasia, if erythropoiesis is to proceed at maximal rates.

Erythroblastic islands are distinct anatomical units allowing direct transfer of ferritin molecule into developing erythroblasts. A patient with Fanconi's anemia who developed acute erythroleukemia and hypotransferrinemia exhibited numerous erythroblastic islands in the bone marrow. This unusual finding in our patient is thought to be in response to an increased demand for iron caused by neoplastic erythropoietic proliferation in the absence of an adequate amount of transferrin.