Phosphorus absorption

All of these actions are directed at increasing serum calcium levels and decreasing serum phosphorus levels, although the activity of calcitriol also increases phosphorus absorption in the GI tract and mobilization from the bone, which can worsen hyperphosphatemia. Calcitriol also decreases PTH levels through a negative feedback loop. These measures are sufficient to correct serum calcium levels in the earlier stages of CKD. 

Phosphate-Binding Agents When serum phosphorus levels cannot be controlled by restriction of dietary intake, phosphate-binding agents are used to bind dietary phosphate in the GI tract to form an insoluble complex that is excreted in the feces. Phosphorus absorption is decreased, thereby... 

Phosphate-binding agents decrease phosphorus absorption from the gut and are first-line agents for controlling both serum phosphorus and calcium concentrations (Table 76-3). 

It is noteworthy that although phosphorus absorption was lower on the high calcium, high polyphosphate diet than on the high calcium, high orthophosphate diet, there was no significant difference between... 

Weanling female rats were used as the test model in these studies. They were housed individually (10 rats/diet) and offered diet and deionized water ad libitum for 5 months. Apparent calcium and phosphorus absorption and urinary Ca and P losses were measured on collections made the last five days each month. Urine volume and pH values were also recorded. Other data (growth response, serum Ca and P levels, femur mineral composition, femur strength and density, and femur histology) were obtained at the end of the 5-month feeding study. Details of this and the analytical methods used are presented elsewhere (8). All data were subjected to appropriate statistical analyses. 

As a brief introductory summary, vitamin D substances perform the following fundamental physiological functions (1) promote normal growth (via bone growth) (2) enhance calcium and phosphorus absorption from the intestine (3) serve to prevent rickets (4) increase tubular phosphorus reabsorpiion (5) increase citrate blood levels (6) maintain and activate alkaline phosphatase m bone (7) maintain serum calcium and phosphorus levels. A deficiency of D substances may be manifested in the form of rickets, osteomalacia, and hypoparathyroidism. Vitamin D substances are required by vertebrates, who synthesize these substances in the skin when under ultraviolet radiation, Animals requiring exogenous sources include infant vertebrates and deficient adult vertebrates, Included there are vitamin D (calciferol ergocalciferol) and vitamin D< (activated 7-dehydrocholesterol cholecalciferol). 

H)2D3 is feedback regulated depending on the need for calcium in the blood. At the present time, 1,25-(0H)2D3 is considered to be the most potent of all the known metabolites of vitamin D3 for controlling calcium and phosphorus absorption from the intestine and mobilization of these elements from the bone when necessary. 

Absorption of 32P-labeled white phosphorus or one of its breakdown products is very rapid following oral administration to animals. Cameron and Patrick (1966) observed 32P systemically in female rats, female rabbits, and male mice for 48 hours following a single oral dose by gavage of 32P-labeled white phosphorus. Absorption of 32P was high in the liver,... 

Various lavage solutions have been suggested, including mineral oil, saline, and dilute copper sulfate solution. Dilute copper sulfate has been suggested for its emetic properties, as well as for its ability to form an apparently inert complex with phosphorus that reduces white phosphorus absorption (Eldad and Simon 1991 Summerlin et al. 1967). 

Vitamin D regulates calcium and phosphorus absorption and deposition and serum alkaline phosphatase levels. The recommended daily allowance is 5 /xg, increasing to 10 to 15 /xg in older age.109 Vitamin D3 is synthesized under UVB irradiation in the skin where it is stored and released into the circulation in a complex with the vitamin D binding protein. In liver it is hydroxylated to 25(OH)-cholecalciferol, the hormonal precursor, followed by another hydroxylation step in the... 

Vitamin D, apart from its availability in the diet, is produced in the body, in response to sunlight striking the skin, and really acts like a hormone. It helps to raise the blood levels of calcium and phosphorus in several ways. It stimulates calcium and phosphorus absorption in the gastrointestinal tract promotes transfer of calcium and phosphorus from bone to blood promotes calcium retention by the kidney. As a hormone it acts 1 entering the cell nucleus and interacting with DNA to regulate protein synthesis. 

OH) 2 cholecalciferol Sterol Intestine Bone Facilitation of calcium and phosphorus absorption increase in bone resorption in conjunction with PTH... 

Antacids neutralize gastric acid, inactivate pepsin, and bind bile salts. Aluminum-containing antacids also suppress HP and enhance mucosal defense. ° G1 adverse effects are most common with antacids and are dose dependent. Magnesium salts cause an osmotic diarrhea, whereas aluminum salts cause constipation. Diarrhea usually predominates with magnesium/aluminum preparations. Aluminum-containing antacids (except aluminum phosphate) form insoluble salts with dietary phosphorus and interfere with phosphorus absorption. Hypophosphatemia occurs most often in patients with low dietary phosphate intake (e.g., malnutrition or alcoholism). Combined treatment with sucralfate may amplify the hypophosphatemia and the potential for aluminum toxicity (see section on sucralfate). 

A wide range of plasma phosphorus concentration has been observed by other workers in primary hyperparathyroidism (C7) and explained in terms of diet and renal excretion. Unlike the calcium concentration, which is normally very constant regardless of dietary intake and urinary excretion, the concentration of inorganic phosphate in plasma is the resultant of the rate of phosphorus absorption from the gut and protein catabolism, on the one hand, and of renal excretion, on the other. Although the parathyroid hormone promotes phosphorus excretion, this is only one of the factors governing plasma phosphate concentration. Plasma phosphate in cases of hyperparathyroidism on a relatively high phosphorus intake may therefore not be distinguishable from that in normal subjects on a lower intake. 

Plant species differ widely in the extent of phosphorus absorption by their roots. Forest trees take up P from insoluble compounds with the help of mycorrhizas, whereas phosphorus is removed from soils by harvested crops ( 6 kg ha in agriculture), erosion and to a small extent by leaching (-0.1 kg ha ) and volatilization as phosphine PH3. In the case of erosion, colloids with their surface-bound P are transported into surface waters, and this leads to the eutrophication of aquatic ecosystems, for example in lakes. Leaching losses occur only in sand and peat soils, and in the case of organic phosphates. Under extreme redox situations - as in some paddy soils - phosphate is reduced to PH3 as a gaseous product. 

Geaee L and Buenel D (1995) Reduction of dietary phosphorus absorption by oral phosphorus binders. Res Commun Mol Pathol Pharmacol 90 389-401. 

Although the PF and BF4 salts of the Te-dication (58) are stable solids, there is as yet no crystallographic data available. In addition to the NMR data given in Table 6 for the dication (58) and the precursor cyclic bis-telluride (59), a phosphorus absorption at S —143.0 (sept, Jpp = 712 Hz relative to H3PO4) is observed in the P NMR of the hexafluorophosphate salt of the dication (58). The drastic downfield shift observed in the Te NMR spectrum (8 1303.7) is consistent with the dication structure <91TL4537>. 

In case phosphorus is absorbed onto the surface of calcite (CaCOs), P change will be controlled mainly by PO4-P. Shukla et al. (1971) compared the difference in phosphorus absorption capacities of the calcium (lime)-rich and calcium-poor sediments in freshwater lakes, and found that the absorption capacity of non-lime sediment was higher than that of lime sediment. 

Vitamin D is required for calcium and phosphorus absorption from the small intestine, their re-absorption in the kidneys and the mineralization process of bones. It thus supports... 

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