Grant R. Bartlett

Iron nucleotides in human and rat red cells

Abstract All of the GTP isolated by ion-exchange chromatography from extracts of rat and human erythrocytes was found to be a 1:1 complex with ferric iron. Small and variable amounts of ferric-ATP were also found. The rat reticulocyte contained much larger amounts of ferric-GTP than the mature cell and a relatively large pool of free GTP, but no ferric-ATP. Ferric-ATP and -GTP were prepared readily by mixing ferric chloride and the nucleotides at room temperature and isolation by ion-exchange chromatography. Ferric ion was found to react preferentially with GTP in competition experiments with ATP. These iron nucleotides may participate in iron transport and hemoglobin synthesis.

ORGANIZATION OF RED CELL GLYCOLYTIC ENZYMES: CELL COAT PHOSPHORUS TRANSFER*

This discussion of human red ccll metabolic organization is limited to problems connected with the uptake and elimination of inorganic phosphate. Tn freshly drawn blood the red cells reveal an almost purely glycolytic metabolism; that is, glucose carbons terminate quantitatively in lactic ac id with minimal routing through pentose phosphate. \Vhile glucose is being consumed a t a constant rate, one finds an unchanging pattern of intermediate phosphorus metabolites inside the cell, including adenosine phosphates and a pool of inorganic phosphate. This equilibrium concentration is sufficient in the case of several of the intermediates to allow isolation in good purity. FIGURE 1 shows the typical pattern we have obtained by Dow-1 ion-ex( hange column chromatographic separation of phosphorus metabolites from the normally metabolizing human red cell. When inorganic orthophosphate was added to blood during this steadystate metabolism the phosphate compounds in the red cell became radioactive at different rates. In a I-hour incubation experiment the relative specihc activities (radioactivity per unit amount of phosphorus) shown in FIGURF 2 were observed. The rounded values refer to the following experimental dctcrminations: first, adenylate, the 3 labile phosphoruses of adenosine diphosphate (ADI’). and adenosine triphosphate (ATP) ; second, hexose, the 6 phosphoruses of the glucose and fructose monophosphates and diphosphates; and third, glycerate, the 3 phosphoruses of rnonophosphoglycerate (RIP(,) and the 2,3-diphosphoglyrerate (2,3-DPG) The difference< in ipecific activity between earh group are large and easily reproducible experimentally. Small differences that were found within each group cannot be diicussed here. ‘The size of each box in the figure i i roughly proportional to the phoiplioru’ “pool” content. The sequence of the phosphate reaction steps must follow the orcicr of decreasing specific activities. The data show that a phosphorus atom from external inorganic phosphate passes through adenylate phosphorus before reaching internal inorganic phosphate, and me have concluded that there is little or no direct contact or exchange between the external and internal inorganic phosphates. The internal iriorgank phosphate equilibrium level and its rate of labeling by P2 may be largely controlled by the phosphorylase reaction : glycogen + inorganic phosphate t--f glucose-t-phosphate. lye have preliminary evidence that a glycogen shunt is an integral part of normal red cell glycolysis. Barring unforeseen me( hanisms, it tan be ( onc luded from the general equation of glycolysis that t lie transfer of phosphorus from exi ernal inorganic

Phosphate compounds in rat erythrocytes and reticulocytes

Abstract The concentrations of glycolytic intermediates, including 2,3-diphosphoglycerate, were similar in rat reticulocytes and erythrocytes. There were striking differences, however, in the content and kind of water-soluble nucleotides. Reticulocytes contained much higher concentrations of ATP, GTP, UTP and CTP and had nucleotides not detected in the mature cell including UDP-acetylhexosamine, guanosine diphosphomannose and an unidentified cytidine compound. A large fraction of the total GTP found in the reticulocyte was in the form of a 1:1 complex of ferric iron with GTP.

Glucosamine and leukemia.

Summary Highly purified glucosamine at dose levels as high as 20 g per day for several days did not influence the course of one patient with acute lymphocytic, one with acute histiomonocytic, one with chronic myelocytic and 2 with chronic lymphocytic leukemias.

Erythrocyte Metabolism in Sickle Cell Anemia.

Summary Several tests of carbohydrate metabolism in the sickle cell anemia erythrocyte did not disclose any abnormality.

Insulin Stimulation of Glycogen Formation in Rat Abdominal Muscle.

Summary If used in thin sheets with a minimum of tissue injury isolated skeletal muscle in the form of the internal oblique muscle of the rat forms more glycogen under the influence of insulin just as does the specialized muscle comprising the diaphragm. Desoxycorticosterone reduces the amount of glycogen formed by incubation with glucose alone as in the case of diaphragm muscle. Skeletal muscle offers new material for further investigation of the action of insulin.