J. D. Torrance

Effect of altitude on oxygen binding by hemoglobin and on organic phosphate levels

The relationship between oxygen dissociation and 2,3-diphosphoglycerate (2,3-DPG) in the red cell has been studied in subjects moving from low to high altitude and vice versa. Within 24 hr following the change in altitude there was a change in hemoglobin affinity for oxygen; this modification therefore represents an important rapid adaptive mechanism to anoxia. A parallel change occurred in the organic phosphate content of the red cell. While this study does not provide direct evidence of a cause-effect relationship, the data strongly suggest that with anoxia, the observed rise in organic phosphate content of the red cell is responsible for increased availability of oxygen to tissues.

Intraerythrocytic adaptation to anemia.

Abstract The role of erythrocyte 2,3-diphosphoglycerate (2,3-DPG) in increasing the availability of hemoglobin oxygen in anemia was investigated. Measurements of 2,3-DPG and of oxygen dissociation (P50) were carried out on 57 normal subjects and 114 subjects with anemia. Twenty normal nonsmoking males had a mean hemoglobin of 15.3 g per 100 ml, a mean DPG of 4.83 mM and a mean P50 of 27.1 mm of mercury. Twenty normal nonsmoking females had a mean hemoglobin lower by 2.6 g per 100 ml, a DPG higher by 0.5 mM and a P50 increased by 0.4 mm of mercury DPG. P50 rose progressively with decreasing hemoglobin concentrations. For each gram of hemoglobin fall, there was a DPG increase of about 0.23 mM and a P50 increase of about 0.30 mm of mercury. Increases in adenosine triphosphate also occurred but, because of the smaller amount involved, had less effect on the oxygen dissociation curve. A rise in inorganic phosphate level had no demonstrable effect, but in vivo pH changes appear of considerable importance. It wa...

THE QUANTITATIVE ESTIMATION OF TOTAL IRON STORES IN HUMAN BONE MARROW

In normal adult males, about 25%o of the body iron content is in storage depots (1). This iron exists in two forms: as a diffuse soluble fraction called ferritin, in which the molecules are dispersed , and as insoluble aggregates of hemosiderin, which can be visualized by conventional micros-copy (2). Although the liver is regarded as the chief storage organ, chemical analyses suggest that it normally contains up to 300 mg (3-5), which is only between one-quarter and one-third of what can be mobilized from total stores when healthy young males are repeatedly phlebotomized (6). Although little is known of the quantities present in other organs, hemosiderin can be seen in the reticuloendothelial cells of the bone marrow (7) and spleen (8), and there is some chemical evidence to indicate that significant amounts of storage iron may be present in skeletal muscles (9, 10). The present study was undertaken to find out how much iron is normally stored in the reticulo-endothelial cells of the bone marrow and to define the extent to which these stores can expand when iron overload is present. In addition, a comparison was made between the concentrations of iron present in the bone marrows and livers of subjects with varying quantities of storage iron. MATERIALS AND METHODS Clinical material. The total iron stores present in bone marrow were estimated in 61 adult subjects undergoing thoracotomy. Forty-one were white and the remainder were Bantu. The individual diagnoses are shown in Table I. The chemical concentrations of storage iron were estimated in the livers and bone marrows of adult Bantu and white subjects dying in the hospital. The Bantu specimens (58 males and 44 females) were obtained from Baragwanath Hospital, Johannesburg, and the white specimens (25 males and 28 females) from the General Hospital, Johannesburg. The use of radioiron as a marrow label. When a tracer quantity of radioiron is injected intravenously, most of it is taken up by the red-cell precursors of the bone marrow (11). This iron is subsequently released over the next few days as part of the hemo-globin of new red cells, and the percentage present in circulation at 10 to 14 days has been used as a measure of the fraction initially taken up by the bone marrow (12). If a specimen of bone marrow is therefore removed between 18 and 24 hours after the injection of the radioiron (i.e., at a time …

The effect of cardiac disease on hemoglobin-oxygen binding

The relation between degree of cardiac functional impairment and changes in hemoglobin-oxygen affinity and 2,3-diphosphoglycerate (2,3-DPG) has been studied in 39 patients with noncyanotic heart disease. A progressive decline in hemoglobin-oxygen affinity was found with worsening cardiac function as assessed by cardiac index, arteriovenous oxygen (A-V O(2)) difference, and cardiac symptoms; this alteration in hemoglobin-oxygen binding represents a significant mechanism for adaptation to the limited oxygen supply imposed by the cardiac lesion. The highly significant correlation of mixed venous blood oxygen saturation (S[unk]V(VO2)) with 2,3-DPG and the position of the oxygen dissociation curve suggests that the level of deoxygenated hemoglobin is an important in vivo regulator of hemoglobin-oxygen affinity.

Acute Change in Hemoglobin Affinity for Oxygen during Angina Pectoris

Abstract The hypothesis that a decrease in hemoglobin affinity for oxygen is a compensory mechanism to increase oxygen delivery to ischemic myocardium was tested in six patients with angina pectoris. Blood was drawn simultaneously from radial artery and coronary sinus. Oxygen tension at 50 per cent saturation (P50) and erythrocytic 2,3-diphosphoglycerate, adenosine triphosphate and pH measured before, during and after angina pectoris produced by atrial pacing showed no significant difference at rest. The longer the duration of angina pectoris, the more coronary-sinus P50 exceeded arterial P50. After four to 10 minutes of angina, the difference was 0.6 to 2.9 mm of mercury. One patient, in whom ST-segment depression and lactate production but no angina pectoris developed, had no change in hemoglobin affinity for oxygen. Decreased hemoglobin affinity for oxygen was not accompanied by change in erythrocytic 2,3-diphosphoglycerate, adenosine triphosphate and pH. The rapid decrease in affinity enhances myocard...

Distribution of Erythrocyte Nucleotides in Pyrimidine 5′‐Nucleotidase Deficiency

Summary. In pyrimidine 5′‐nucleotidase deficiency, erythrocytes contain elevated levels of pyrimidine nucleotides. The composition of this nucleotide pool was examined by ion exchange chromatography on Dowex formate columns using a linear ammonium formate elution gradient. In contradistinction to normal erythrocytes, adenine nucleotides accounted for only 32% of the nucleotide pool. The remainder consisted of 50% cytidine and 16% uridine nucleotides. The remaining 2% was not identified. The most abundant compound appeared to be UDP glucose whilst high levels of CTP, CMP and an unidentified cytidine compound less polar than CMP accounted for most of the cytidine nucleotide pool. The possibility that the abnormal nucleotides were due to an elevated reticulocyte count was excluded and it was also shown that erythrocytes from subjects heterozygous for pyrimidine 5′‐nucleotidase deficiency did not have detectable levels of the abnormal nucleotides.

Failure of transferrin to enhance iron absorption in achlorhydric human subjects

There is evidence in experimental animals that transferrin, produced either by gastrointestinal cells or derived from bile, mediates the luminal absorption of iron. The applicability of these findings to human subjects was tested by administering diferric transferrin labelled with 3 mg 59Fe to seven patients with pernicious anaemia. Achlorhydric subjects were chosen to ensure that the iron transferrin complex did not dissociate in the stomach. The geometric mean absorption of 1.4% was similar to that of 3 mg iron given as ferric chloride (1.9%) and much less than that of ferrous ascorbate (18.9%). These findings suggest that transferrin does not play a physiological role in the absorption of iron in human subjects.

Can Iron Fortification of Flour Cause Damage to Genetic Susceptibles (Idiopathic Haemochromatosis and β-Thalassaemia Major)?

Currently under consideration in the U.S.A. is a proposal to increase the level of iron fortification of flour from its current figure of 13.0-16.5 mg per pound to 40 mg per pound (Waddell et al. , 1972). The debate engendered by these proposals has been concerned with two aspects. On the one hand there is the question of efficacy and on the other the question of safety (Crosby, 1973). The purpose of the present paper is to attempt to predict the answer to the second question. At particular risk are those individuals who suffer from ‘iron-loading’ states. In the genetic disorder, idiopathic haemochromatosis, excessive amounts of iron are absorbed from a normal diet, while in the other group of conditions, which includes refractory anaemias such as β thalassaemia major, the iron is derived both from donor blood and from excessive absorption from the gut (Bothwell and Finch, 1962). While the number of subjects at risk is not accurately known, it has been estimated that there are currently about 20,000 individuals with idiopathic haemochromatosis and 5000 with β thalassaemia major in the United States.

Erythrocyte pyrimidine 5'-nucleotidase.

Summary In this study 31 family members of a patient with erythrocyte pyrimidine 5′‐nucleotidase deficiency were studied. The activity of this enzyme in their erythrocytes is compared with levels in normal subjects and the problems surrounding heterozygote detection are discussed. The mean erythrocyte pyrimidine 5′‐nucleotidase activity in 158 normal fresh blood samples was 130·SD 29·8 mU/gHb. There was no significant difference between males and females. The enzyme level in a patient with non‐spherocytic haemolytic anaemia was 6 mU/gHb. Of 31 relatives of the enzyme deficient patient examined five were clearly heterozygous for the enzyme defect. Their enzyme levels were below 50 mU/gHb. The father, who is an obligatory heterozygote, had an enzyme level of 87 mU/gHb which falls within the low values of the normal range, the distribution of enzyme activity in 26 family members having enzyme activities greater than 50 mU/gHb suggests that six of these may be carriers of the defective gene. We were unable to identify carriers by enzyme kinetic studies, electrophoresis, chromatographic examination of acid extractable nucleotides or measurement of enzyme levels in young and old erythrocyte populations. The last‐mentioned technique showed that erythrocyte 5′‐nucleotidase activity in reticulocytes may be as high as 1785 mU/gHb and declines rapidly as the cell ages reaching about 50 mU/gHb in the oldest cells. Blood samples which had been stored frozen were examined to see whether such samples were satisfactory for population studies. The mean enzyme activity in 151 blood samples stored frozen for more than 12 months was 153·SD 44·7 mU/gHb. The increase in enzyme levels in the frozen samples appears to be greatest in samples showing haemolysis. In spite of the increased enzyme level frozen samples could be used to detect subjects with enzyme deficiency and some heterozygotes.

Problems encountered in measuring erythrocyte pyrimidine 5′-nucleotidase activity☆

Abstract Pyrimidine 5′-nucleotidase activity in hemolysates may be measured either by the inorganic phosphate released from CMP substrate or by the [14C]cytidine formed when [14C]CMP is substrate. A 90% inhibition of the enzyme by adenosine, inosine, guanosine, adenine, or guanine has been reported. These results were obtained with the chemical assay and we could not confirm them with the radioactive assay. We also found no inhibition by adenosine or inosine in the chemical assay when purified enzyme replaced hemolysate. Evidence is presented that the apparent inhibition of the chemical assay is due to other hemolysate enzymes which incorporate inorganic phosphate released from CMP into organic compounds. We also could not show inhibition by adenine or guanine even in the chemical assay with hemolysate. Thus the nucleosides and bases mentioned above do not appear to be inhibitors of erythrocyte pyrimidine 5′-nucleotidase activity.