Phosphates Circulation

Phosphate is found in all parts of the body but is most abundant in the bones and teeth (85 percent). Phosphate circulates in the blood in a protein-bound form (12 percent), a complexed form (33 percent), and an ionized form (55 percent), which is the physiologically active form. However, most laboratory values represent the total phosphate level. The phosphate level will fluctuate during the day based on physiologic activity that may increase cellular use. The reported level may be low because more phosphate is intracellular than usual or may be high because more phosphate has moved out of the cells than usual in response to some temporary situation. Thus a fiiU assessment is important to ensure that the proper treatment is provided. For example, if phosphate levels are high, calcium levels should be assessed to determine if the elevation might be due to a release of calcium and phosphate from bone. Treatments then are planned to address the actual cause of the imbalance. 

Both pyridoxal and the phosphate circulate in the bloodstream the phosphate is dephosphorylated by extracellular alkaline phosphatase, and tissues take up pyridoxal by carrier-mediated diffusion, followed by metabolic trapping as phosphate esters. Pyridoxine and pyridoxamine phosphates are oxidized to pyridoxal phosphate (Figure 1). 

A circulating fluidized-bed boiler, using raw shale oil as a feedstock, is being used to supply process heat for the phosphate operations and to operate a 100-MW power plant. Scale-up in the 1990s should increase the electric power generation to 1000 MW (71). 

Three types of methods for phosphate analyses have been studied with the aims of monitoring the distribution and circulation of orthophosphate and observing the chemical forms of phosphoms compounds occurring in the natural water environment. 

Phosphorus also occurs in all living things and the phosphate cycle, including the massive use of phosphatic fertilizers, is of great current interest.O 20) -pj.jg movement of phosphorus through the environment differs from that of the other non-metals essential to life (H, C, N, O and S) because it has no volatile compounds that can circulate via the atmosphere. Instead, it circulates via two rapid biological... 

Temperature of the system When inhibitors are used in the 0-100°C range it is usually found that higher concentrations become necessary at the higher temperatures Other inhibitors can lose their effectiveness altogether as the temperature is raised. A prime example of this is the polyphosphate type of inhibitor. This is effective in circulating systems at temperatures below about 40°C, but at higher temperatures reversion to orthophosphate can occur and this species is ineffective at the concentrations at which it will then be present. If calcium ions are present, additional loss of inhibitor will occur due to calcium phosphate precipitation. 

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. 

When boiler cleaning takes place, it often is followed by the circulation of a hot alkaline phosphate solution to provide adequate passivation of metal surfaces. (A typical formulation may also include sodium gluconate, antifoam, and dispersants.)... 

Anionic Association Polymer. Another type of lost circulation agent is a combination of an organic phosphate ester and an aluminum compound, for example, aluminum isopropoxide. The action of this system as a fluid loss agent seems to be that the alkyl phosphate ester becomes crosslinked by the aluminum compound to form an anionic association polymer, which serves as the gelling agent [1488]. 

M. L. Allan and L. E. Kukacka. Calcium phosphate cements for lost circulation control in geothermal. Geothermics, 24(2) 269-282, April 1995. 

Dobson, E. L., Finkelstein, L. J., Finney, C. R. and Kelly, L. S. (1966). Particulate chromic phosphate Colloid characteristics suitable for measurement of liver circulation, page 477 in Radioactive Pharmaceuticals, AEC Symposium Series No. 6, Report No. CONF-651111, Andrews, G. A., Kniseley, R. M. and Wagner, H. N., Jr., Eds. (National Technical Information Service, Springfield, Virginia). 

Hemolytic anemia results from decreased RBC survival time due to destruction in the spleen or circulation. The most common etiologies are RBC membrane defects (e.g., hereditary spherocytosis), altered Hb solubility or stability (e.g., sickle cell anemia [see Chap. 34] and thalassemias), and changes in intracellular metabolism (e.g., glucose-6-phosphate dehydrogenase deficiency). Some drugs cause direct oxidative damage to RBCs (see Appendix 3). 

The leucocyte method estimates pyridoxal phosphate in isolated leucocytes it is based on a coenzyme-catalyzed tyrosine decarboxylase system from S. faecalis (B32). Enough data are not yet on hand to evaluate this method. The determination of circulating or available vitamin Ba should offer a more direct approach. 

---