Phosphate in blood

Figure 3.18 Adenosine phosphates in blood on vinyl polymer column. Conditions column, Asahipak GS320 (vinyl alcohol copolymer gel), 50 cm x 7.6 mm i.d. eluent, 0.1 M sodium phosphate buffer containing 3 M sodium chloride pH 7.0 flow rate, 1.0 ml min-, detection, UV 260 nm. Peaks 1, haemoglobin 2, adenosine triphosphate 3, adenosine diphosphate and 4, adenosine monophosphate.

Phosphorus is a critically important element in every cell of the body and also in the form of hydroxyapatite in bone and in all other functions as phosphate. The concentration of phosphate in blood is 1.0 to 1.5 mmol/L existing as H2P0( and HPOl" the equilibrium between the two acts as a proton buffer... 

Phosphorus, in combination with calcium, is important for bone mineralization, as well as for many chemical reactions in the body (NAS 1980A). Like calcium, most of the body s phosphorus (80-90%) is found in bones. The remaining 10 to 20% exists as soluble phosphate in blood, cells, lipids, proteins, carbohydrates, and energy-transfer enzymes (NAS 1980A). 

Riera, M., Fuster, J.F., and Palacios, L., 1991, Role of erythrocyte organic phosphates in blood oxygen transport in anemic quail. Am. J. Physiol. 260 R798-R803. 

Human phosphate binding protein (HPBP), an apolipoprotein that binds inorganic phosphate in blood, was serendipitously discovered. Its three-dimensional structure and complete amino acid sequence were solved (Morales et al, 2006 Diemer et al, 2008). The conditions found to separate HPBP and PONl in vitro indicated that HPBP is strongly associated with PONl (Renault et al, 2006). Moreover, the stabilization of the active form(s) of human PONl by HPBP suggests that HPBP could be a functional chaperone for PONl (Rochu et al, 2007b, c). 

Calculate the ratio of dihydrogen phosphate/hydrogen phosphate in blood at pH 7.4. The is 6.3 X ICE8. 

The fluorimetric determination of pyridoxal and pyridoxal-5-phosphate in blood serum based on their different oxidation rates in the presence of cyanide [49]. 

The level of inorganic phosphate in blood is controlled by a balance of various factors such as phosphatase activity, parathyroid hormone, and vitamin D. 

At the reaction of blood, pH 7-4, this acid carbonate system is not exerting its maximum effect, but as the acidity of the blood increases the buffer action becomes more powerful, and thus constitutes an important alkaline reserve of the organism. The acid phosphate system is more effective at pH 7-4, but the low concentration of phosphates in blood renders the system almost insignificant. 

Table 2 Approximate percentage (%) distributions of calcium and phosphate in blood...

Three hormones regulate turnover of calcium in the body (22). 1,25-Dihydroxycholecalciferol is a steroid derivative made by the combined action of the skin, Hver, and kidneys, or furnished by dietary factors with vitamin D activity. The apparent action of this compound is to promote the transcription of genes for proteins that faciUtate transport of calcium and phosphate ions through the plasma membrane. Parathormone (PTH) is a polypeptide hormone secreted by the parathyroid gland, in response to a fall in extracellular Ca(Il). It acts on bones and kidneys in concert with 1,25-dihydroxycholecalciferol to stimulate resorption of bone and reabsorption of calcium from the glomerular filtrate. Calcitonin, the third hormone, is a polypeptide secreted by the thyroid gland in response to a rise in blood Ca(Il) concentration. Its production leads to an increase in bone deposition, increased loss of calcium and phosphate in the urine, and inhibition of the synthesis of 1,25-dihydroxycholecalciferol. 

PTH is the most important regulator of bone remodelling and calcium homeostasis. PTH is an 84-amino acid polypeptide and is secreted by the parathyroid glands in response to reductions in blood levels of ionised calcium. The primary physiological effect of PTH is to increase serum calcium. To this aim, PTH acts on the kidney to decrease urine calcium, increase mine phosphate, and increase the conversion of 25-OH-vitamin D to l,25-(OH)2-vitamin D. PTH acts on bone acutely to increase bone resorption and thus release skeletal calcium into the circulation. However, due to the coupling of bone resorption and bone formation, the longer-term effect of increased PTH secretion is to increase both bone resorption and bone formation. 

N7. Ninfali, P., Bresolin, N., Baronciani, L., Fortunato, F., Comi, G., Magnani, M., and Scarlato, G., Glucose-6-phosphate dehydrogenase Lodi844C A study on its expression in blood cells and muscle. Enzyme 45, 180-187 (1991). 

We used outdated human CPD (citrate-phosphate-dextrose) blood from the Dayton Community Blood Center. At 21 days, CPD blood still retains 78% survival of the red blood cells and would fairly well simulate in vivo physiological conditions. During these tests, many enzymes and proteins may denature and/or precipitate. Even after suffering that trauma, the resulting fluid is more suitable for material testing than other pseudo-physiological fluids, since it still contains most of the salts, lipids, hormones, oligomers, nucleotides, saccharides, etc., found in whole blood in vivo. 

Valproic acid has been determined in human serum using capillary electrophoresis and indirect laser induced fluorescence detection [26], The extract is injected at 75 mbar for 0.05 min onto a capillary column (74.4 cm x 50 pm i.d., effective length 56.2 cm). The optimized buffer 2.5 mM borate/phosphate of pH 8.4 with 6 pL fluorescein to generate the background signal. Separation was carried out at 30 kV and indirect fluorescence detection was achieved at 488/529 nm. A linear calibration was found in the range 4.5 144 pg/mL (0 = 0.9947) and detection and quantitation limits were 0.9 and 3.0 pg/mL. Polonski et al. [27] described a capillary isotache-phoresis method for sodium valproate in blood. The sample was injected into a column of an EKI 02 instrument for separation. The instrument incorporated a conductimetric detector. The mobile phase was 0.01 M histidine containing 0.1% methylhydroxycellulose at pH 5.5. The detection limit was 2 pg/mL. 

Patients with end-stage renal disease hyperphosphatemia ineffectively filter excess phosphate that enters the body in the normal diet.278 Elevated phosphate produces the bone disorder renal osteodystrophy. Skeletal deformity may occur, possibly associated with cardiovascular disease. Calcium deposits may further build up around the body and in blood vessels creating further health risks. The use of lanthanum carbonate is being promoted as an alternative to aluminum-based therapies.279,280 Systemic absorption, and cost have produced a clinical candidate, Fosrenol (AnorMED), an intriguing use of a lanthanide compound in therapy. 

Clinical chemistry, particularly the determination of the biologically relevant electrolytes in physiological fluids, remains the key area of ISEs application [15], as billions of routine measurements with ISEs are performed each year all over the world [16], The concentration ranges for the most important physiological ions detectable in blood fluids with polymeric ISEs are shown in Table 4.1. Sensors for pH and for ionized calcium, potassium and sodium are approved by the International Federation of Clinical Chemistry (IFCC) and implemented into commercially available clinical analyzers [17], Moreover, magnesium, lithium, and chloride ions are also widely detected by corresponding ISEs in blood liquids, urine, hemodialysis solutions, and elsewhere. Sensors for the determination of physiologically relevant polyions (heparin and protamine), dissolved carbon dioxide, phosphates, and other blood analytes, intensively studied over the years, are on their way to replace less reliable and/or awkward analytical procedures for blood analysis (see below). 

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