Blood from patients with erythrocytosis secondary to arterial hypoxemia due either to congenital heart disease or to chronic obstructive pulmonary disease was shown to have a decreased affinity for oxygen; the average oxygen pressure required to produce 50% saturation of hemoglobin with oxygen was 29.8 mm Hg (average normal, 26.3 mm Hg). Such a displacement of the blood oxygen equilibrium curve promotes the release of oxygen from blood to the tissues. Studies were also performed upon blood from a man with complete erythrocyte aplasia who received all of his red cells by transfusion from presumably normal persons. With mild anemia (hematocrit, 28%), the affinity of his blood for oxygen was slightly diminished (an oxygen pressure of 27.0 mm Hg was required to produce 50% saturation of hemoglobin with oxygen). With severe anemia (hematocrit, 13.5%), however, his blood had a markedly decreased oxygen affinity (an oxygen pressure of 29.6 mm Hg was required to produce 50% saturation of hemoglobin with oxygen). We conclude that patients with various conditions characterized by an impairment in the oxygen supply system to tissues respond with a diminished affinity of their blood for oxygen. Although the mechanism which brings about this adaptation is not known, the displacement of the oxygen equilibrium curve is associated with an increase in heme-heme interaction. The decrease in blood oxygen affinity need not occur during erythropoiesis, but may be imposed upon mature circulating red cells.

Adult↗

PubMed1967

Nitrite metabolism by skeletal muscle mitochondria in relation to haem pigments.

Explore the source record for details and available documents.

Animals↗

PubMedDate not supplied

The collaborative evaluation of a procedure for the determination of N-nitroso compounds as a group.

Two collaborative studies have been made of the method devized for the determination of N-nitroso compounds as a group, which involves their selective denitrosation with hydrogen bromide in glacial acetic acid, followed by the measurement of the nitric oxide liberated using a chemiluminescence analyzer, such as the TEA. Considerable variation was evident between the results in the first study, most of the values reported being low. This situation undoubtedly arose from the carry-over of traces of hydrogen bromide from one determination to the next, which resulted in premature denitrosation. The precision and consistency of the results were greatly improved in the second study, for which additional precautions had been recommended. All of the six participating laboratories reported reasonably consistent values, the coefficients of variation being 27.9% and 21.1% respectively, at the levels of spiking of N-nitrososarcosine equivalent to 32.9 ng and 146.4 ng of nitric oxide.

Indicators and Reagents↗

PubMedDate not supplied

A rapid method for the determination of nitrate and nitrite by chemiluminescence.

Nitrite and nitrate + nitrite can be determined by selective chemical reduction to nitric oxide which is measured using a chemiluminescence analyser. The reducing agents are sodium iodide in acetic acid for nitrite and ferrous ammonium sulphate-ammonium molybdate for nitrate + nitrite. The concentrations of the reducing agents have been optimized to obtain the maximum yield of nitric oxide and the minimum coefficient of variation. Under these conditions, it is possible to inject repeated samples into the refluxing reducing agents and to obtain rapid evolutions of nitric oxide from which the determinations can be made. Nitric oxide has also been produced using the nitrite reagents from organic nitrites, a S-nitrosothiol, a pseudonitrole and N-nitrosamines. Similarly, an organic nitrate and some C-nitroso compounds respond to the method for nitrate but only to the extent of a yield of nitric oxide of about 10% of the theoretical. Very low or zero responses were evident from aliphatic and aromatic C-nitro compounds but not omega-N-nitroarginine which gave a large yield of nitric oxide using the reagents for nitrate. In general, however, concentrations of nitrate will be in considerable excess of those of related compounds which would interfere with the determinations. Nitrate can be determined either by difference in its mixtures with nitrite or by prior removal of the nitrite using ascorbic acid provided oxygen and nitric oxide are removed by degassing with nitrogen.

Indicators and Reagents↗

PubMedDate not supplied

Reactions of nitrate and nitrite in foods with special reference to the determination of N-nitroso compounds.

The stabilities of nitrate and nitrite in food systems and their reactions in such matrices are reviewed. Particular reference is made to reactions with haem proteins, smoke components and amines in foods, and the chemistry of formation of N-nitroso compounds from food components is discussed. Finally, the methodology available for determination of both volatile and non-volatile N-nitroso compounds is addressed.

Catalysis↗