Blood phosphate

Decrease blood calcium Increase blood calcium decrease blood phosphate activation of vitamin D 3 "Fight-or-flight" response reinforces effects of the sympathetic nervous system Reabsorption of sodium excretion of potassium... 

Parathyroid hormone stimulates bone resorption by increasing the number and activity of osteoclasts. This demineralization process in the bone releases calcium and phosphate into the blood. Although the action of PTH on the bone appears to increase blood phosphate, its action on the kidney, which increases phosphate excretion in the urine, more than compensates for this increase and the net effect is a decrease in serum phosphate. 

I. A 25-year-olcl female suspected of having vitamin D-resistant rickets has decreased blood phosphate levels. Aside from high-dose vitamin D and oral phosphate, an alternative therapeutic approach might be the use of which of the following ... 

The polypeptide parathormone is released from the parathyroid glands when plasma Ca + level falls. It stimulates osteoclasts to increase bone resorption in the kidneys, it promotes calcium reabsorption, while phosphate excretion is enhanced. As blood phosphate concentration diminishes, the tendency of calcium to precipitate as bone mineral decreases. By stimulating the formation of vit D hormone, parathormone has an indirect effect on the enteral uptake of Ca + and phosphate. In parathormone deficiency, vitamin D can be used as a substitute that unlike parathormone, is effective orally. 

A normal adult has a total body phosphorus content of 700-800 g [1]. The majority of phosphate is present in bone, although approximately 15% is distributed outside of the skeleton where it is present in the form of inorganic phosphate in extra-cellular fluid and organic phosphates within cells, such as adenosine triphosphate (ATP), nucleic acids, and membrane phospholipids. As such, phosphorus plays a vital role in numerous cell processes including cell energetics, cell membrane formation, and DNA RNA synthesis, to name a few. Within blood, phosphate exists mainly in two forms, HPO and HjPO. These two anions are important serum buffers and their relative concentrations are determined by the serum pH. 

Blood creatine phosphokinase (CPK) - increased Blood creatinine - increased Blood phosphate - decreased Blood potassium - decreased Blood urea nitrogen - increased... 

A. Increased levels of blood phosphate ion interact with sensors on the membrane of parathyroid cells to stimulate parathyroid hormone... 

The H2PO4/HPO4 pair is the principal buffer in cells. In blood, phosphate ion levels are inadequate for buffering, and a different system operates. 

As blood calcium levels fall, PTH is released from the parathyroid gland and acts directly upon the kidney and bone as well as indirectly on the intestines. The renal actions of PTH, mostly mediated by cAHP, are summarized in Table I. These direct renal PTH actions, therefore, elevate blood calcium levels by enhancing calcium reabsorption and by lowering blood phosphate concentrations and pH. The latter two actions of PTH allow calcium levels to rise to a greater extent without precipitating calcium phosphate. 

However, direct experiments show clearly that phosphate absorption is rapid and complete in vitamin D deficiency, provided no calcium is present. The low blood phosphate in rachitic rats is due to (1) low P diet and (2) the prevention of phosphate absorption by calcium. 

Riley, R. F. Metabolism of phosphorylcholine. II. Partition of phosphorylcholine phosphorus between blood phosphate fractions. III. Partition of phosphorylcholine phosphorus between tissues. IV. Distribution of phosphorylcholine phosphorus in tissue lipids. J. biol. Chem. 163, 535-49 (1944). 

HypophosphstemiB lAlso see PHOSPHORUS and VITAMIN 0.1 Defect in kidney tubules low blood phosphate blood ttalcium level oormat rickets and dwarfism transmitted on the se chromosomes. Large doses of vitamin D oral phosphorus. 

Organic.—Glycerophosphates and hexosephosphates phos-phatides phosphoproteins, and unidentified compounds. In plants, phosphorus occurs in phosphoproteins and in phytin— the Ca Mg salt of inositol-phosphoric acid. Various forms of muscle and blood phosphates are recognised analytically in animal tissues. 

Hypophosphatcemia.— The rise in blood calcium is associated with a fall in blood phosphate. 

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