Bicarbonates in blood

EXPERIMENTS DETERMINATION OF BICARBONATE IN BLOOD USING BACK-TITRATION... 

Bicarbonate in blood is difficult to determine as such. There are... 

Carbon dioxide devices were originally developed by Severinghaus and Bradley (59) to measure the partial pressure of carbon dioxide in blood. This electrode, still in use today (in various automated systems for blood gas analysis), consists of an ordinary glass pH electrode covered by a carbon dioxide membrane, usually silicone, with an electrolyte (sodium bicarbonate-sodium chloride) solution entrapped between them (Figure 6-17). When carbon dioxide from the outer sample diffuses through the semipermeable membrane, it lowers the pH of the inner solution ... 

This interpretation is in conflict with some published discussions of the source of bone carbonate, which suggest that bone carbonate gives us a sample of energy somces (Krueger and Sulhvan 1984), by which is meant carbohydrates and fats (e.g., Ambrose and Norr 1993). It should be clear from the previous discussion that very little partitioning of carbon somces can occm. Bicarbonate in the blood is derived from essentially all the carbon atoms in the diet, including proteins, in proportion to their abimdance in the diet all foods are energy sources . Minor deviations from this arise due to (1) Tissue... 

This isotonic volume expander contains sodium, potassium, chloride, and lactate that approximates the fluid and electrolyte composition of the blood. Ringer s lactate (also known as lactated Ringer s or LR) provides ECF replacement and is most often used in the perioperative setting, and for patients with lower GI fluid losses, burns, or dehydration. The lactate component of LR works as a buffer to increase the pH. Large volumes of LR may cause metabolic alkalosis. Because patients with significant liver disease are unable to metabolize lactate sufficiently, Ringer s lactate administration in this population may lead to accumulation of lactate with iatrogenic lactic acidosis. The lactate is not metabolized to bicarbonate in the presence of liver disease and lactic acid can result. 

This reaction is essential in maintaining a constant pH in blood by the bicarbonate buffer system. Carbonic anhydrase, which contains a single zinc atom in its structure, has a molecular weight of about 30,000. In this structure, zinc is surrounded tetrahedrally by three histidine molecules and one water molecule. The exact role of the catalyst is not known, but it is believed to involve hydrolysis that can be represented as... 

Henderson-Hasselbalch Equation Titration Curves p/—Isoelectric Point The Bicarbonate Buffer Imbalance in Blood pH Acidosis and Alkalosis... 

Fluorescent pH indicators offer much better sensitivity than the classical dyes such as phenolphthalein, thymol blue, etc., based on color change. They are thus widely used in analytical chemistry, bioanalytical chemistry, cellular biology (for measuring intracellular pH), medicine (for monitoring pH and pCC>2 in blood pCC>2 is determined via the bicarbonate couple). Fluorescence microscopy can provide spatial information on pH. Moreover, remote sensing of pH is possible by means of fiber optic chemical sensors. 

Lithium salts, generally in the form of the carbonate or bicarbonate, are rapidly absorbed from the gastrointestinal tract and reach a peak plasma concentration after 2- hours. Extreme fluctuations in blood lithium levels, which are associated with side effects such as nausea, diarrhoea and abdominal cramp, are reduced by using sustained release preparations. Lithium is not protein bound and therefore is widely distributed throughout the body water, which accounts for the adverse effects it has on most organ systems should it reach toxic levels. To avoid toxicity, and ensure optimal... 

The excessive amount of bicarbonate in the blood means that blood has a much greater capacity to neutralize acids. Many acids accumulate in the blood during strenuous activity, for example lactic acid. Excretion of bicarbonate through the kidneys and the removal of carbon dioxide through respiration also regulate the carbonic acid/ bicarbonate blood buffer. 

The human body is a remarkable machine. It relies on a variety of safeguards to keep blood pH constant. Our blood constitutes a buffer system — meaning, it has components that can react with excess base or excess acid. Carbon dioxide, which is produced by the metabolism of food, dissolves in blood to produce carbonic acid, and carbonic acid can neutralize any excess base. The bicarbonate ion, also present in blood, will promptly take care of any surplus acid. The level of carbon dioxide in the blood adjusts to a body s rate of respiration. If blood pH drops — which actually means that the blood has... 

The blood pH may return to normal in adults with mild overdoses. However, the blood pH can drop too far in children or more severely poisoned adults, resulting in metabolic acidosis. A lower buffering capacity or plasma protein-binding capacity may underlie the increased susceptibility to acidosis in children. Excretion of bicarbonate also means the bicarbonate in the blood is lower, and hence, there is an increased likelihood of metabolic acidosis. 

Tin metabolic acidosis (p. 652) there is an increase in glutamine processing by the kidneys. Not all the excess NH4 thus produced is released into the bloodstream or converted to urea some is excreted directly into the urine. In the kidney, the NH% forms salts with metabolic acids, facilitating their removal in the urine. Bicarbonate produced by the decarboxylation of a-lcetoglutarate in the citric acid cycle can also serve as a buffer in blood plasma. Taken together, these effects of glutamine metabolism in the kidney tend to counteract acidosis. ... 

The comparison of Km s with physiological substrate concentrations is difficult in many cases due to a lack of knowledge of the concentrations, but there are some well-characterized examples. One particular case is carbonic anhy-drase, because the concentrations of carbon dioxide and bicarbonate in the blood are easily measured. Under physiological conditions, the enzyme is only about 6% saturated with each substrate, and the KM of carbon dioxide is too high to be measured.26... 

We see that dihydrogenphosphate will not react with bicarbonate in an acid-base reaction. This also means they are compatible with each other in solution (e.g., blood). Whiles these ions serve other purposes, (e.g., dihydrogen phosphate is the inorganic phosphate in metabolism), both of these ions have acid-base properties and they assist us in maintaining a constant pH. 

Thus the drop in ammonia content of plasma in alkalosis may be related to the pH effect on urea synthesis rather than to the alterations in permeability caused by changes in pNHs. The treatment of hepatic coma by acidification with C02 would lower pH, inhibiting synthesis of urea. This would cause a rise in blood ammonia. The same type of change could be brought about by infusion of HC1, which would have a double effect on urea synthesis by lowering both pH and bicarbonate. It does not appear necessary to invoke a penetration hypothesis to explain the... 

Gas-selective electrodes are a particularly important application of the glass electrode. For example, the carbon dioxide electrode is a self-contained system with a glass electrode and a concentric silver-silver chloride electrode enclosed by a C02 permeable membrane. The latter holds a thin film of bicarbonate solution in contact with the glass membrane, which provides a junction to the silver/silver chloride reference electrode. The electrode, which is illustrated schematically by Figure 2.2, has found extensive application in monitoring C02 levels in blood and probably will find increasing application in other systems that require continuous measurement of C02 partial pressures. The electrode response is based on the reaction... 

In mammals the bicarbonate ion, IICOT, is used as a buffer in blood and is catalysed by the zinc-containing enzyme carbonic anhydrase ... 

Mineralocorticoids help control the body s water volume and concentration of electrolytes, especially sodium and potassium. Aldosterone acts on kidney tubule cells, causing a reabsorption of sodium, bicarbonate, and water. Conversely, aldosterone decreases reabsorption of potassium, which is then lost in the urine. [Note Elevated aldosterone levels may cause alkalosis and hypokalemia, whereas retention of sodium and water leads to an increase in blood volume and blood pressure (see p. 180). Hyperaldosteronism is treated with spironolactone (see p. 232).]... 

Bicarbonate ions are freely filtered by the glomerulus. The concentration of bicarbonate in the tubular fluid is equivalent to that of plasma. If bicarbonate were not reabsorbed the buffering capacity of the blood would rapidly be depleted. 

Once absorbed into the system circulation, uranium undergoes chemical transformations to complex with the blood. Uranium in the trivalent form will oxidize to the hexavalent species to form uranyl ions, which form soluble complexes with bicarbonate, citrate, or proteins in the plasma (Chevari and Likhner, 1968 Cooper et al, 1982 Stevens et al, 1980). The distribution of uranium in the blood is approximately 47% complexed with bicarbonate in plasma, 32% bound to plasma proteins, and 20% bound to erythrocytes (Chevari and Likhner, 1968, 1969). 

Uranium is usually found in compounds which can be metabolized and recomplexed to form other compounds. In body fluids, tetravalent uranium is likely to oxidize to the hexavalent form followed by formation of uranyl ion. Uranium generally complexes with citrate, bicarbonates, or protein in plasma (Cooper et al. 1982 Bounce and Flagg 1949 Stevens et al. 1980). The stability of the carbonate complex depends on the pH of the solution, which will differ in different parts of the body (BEIRIV 1988). The low-molecular-weight bicarbonate complex can be filtered at the renal glomerulus, and be excreted in urine at levels dependent on the pH of the urine. The uranium bound to the protein (primarily transferrin) is less easily filtered and is more likely to remain in blood. In the blood, the uranyl ion binds to circulating transferrin, and to proteins and phospholipids in the proximal tubule (Wedeen 1992). 

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