Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.1.3.1 (alkaline phosphatase)
47,916 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Bone ECF is separated from the general ECF by a functional membrane which has been shown to limit the mineralization of embryonic tibiae and to selectively pump Ca out of the bone ECF. Energy to run this pump may be derived from ATP hydrolyzed by Ca-2+-stimulated ATPase, an enzyme activity which bone alkaline phosphatase may possess. The data suggest that PTH rapidly and selectively increases Ca pumping possibly by increasing ATPase activity in the bone cell cytosol through increased Ca influx and by increasing the intracellular ATPase level through inhibited secretion or excretion of the enzyme.
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PMID:Cellular control of calcium movements in bone. Interrelationships of the bone membrane, parathyroid hormone and alkaline phosphatase. 12 41

Two metabolically distinct types of bone cell populations were isolated from mouse calvaria by a repetitive digestive procedure with a mixture of collagenase and trypsin. Cells released early in the digestion showed approximately two-fold increases in cAMP when treated with either parathormone or calcitonin. These populations were denoted CT type. Later eluting cells showed larger parathormone-induced increases in cAMP but did not respond to calcitonin. These populations were denoted PT type. Six metabolic and enzymatic activites were measured in the two types of populations: acid and alkaline phosphatases, hyaluronate synthesis, citrate decarboxylation, prolyl hydroxylase, and general protein synthesis. Although each of these activites was present in both cell types, the basal levels of acid phosphatase and hyaluronate synthesis were higher in the CT cells, whereas alkaline phosphatase, citrate decarboxylation, and prolyl hydroxylase were higher in te PT cells. Parathormone stimulated acid phosphatase and hyaluronate synthesis by 100-200% only in the CT cells; in inhibited alkaline phosphatase, citrate decarboxylation, and prolyl hydroxylase by 75-90% only in the PT cells. Calcitonin alone had no effect on any of these activities other than cAMP production, but in inhibited the action of parathormone in the CT cells. The sensitivities, time courses of development,and magnitudes of these hormonal effects were similar to those observed previously in intact calvaria, indicating that the isolated cell system is a reliable model for the study of bone metabolism. Based on the metabolic responses of the cells, we postulate that the CT type of populations is enriched in osteoclasts and, possibly, osteocytes, and the PT type of population is enriched in osteoblasts.
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PMID:Biochemical characterization with parathormone and calcitonin of isolated bone cells: provisional identification of osteoclasts and osteoblasts. 18 58

Indices of calcium and phosphorus metabolism were studied in 3 children with osteopetrosis before and after infusion of bovine parathyroid hormone extract. Basal plasma concentrations of calcium, alkaline phosphatase and 25-hydroxy vitamin D tended to be low. Plasma immunoreactive PTH levels were at the upper normal range in two patients. A marked increase in urinary cyclic AMP in all patients was solely due to an increase in the nephrogenous cAMP. After vitamin D treatment urinary cAMP was essentially unchanged with the same preponderance of nephrogenous cAMP. Following PTH infusion plasma cAMP showed a brisk rise. There was also a prompt rise in urinary cAMP and a distinct decrease in the calcium to sodium clearance ratio indicating increased calcium reabsorption. Phosphaturic effect was only observed when PTH was given in the highest dose level. The findings are consistent with a state of low grade hyperparathyroidism which could not be related to the plasma levels of 25-hydroxy vitamin D or calcium.
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PMID:Acute response of parathyroid hormone in congenital osteopetrosis. 23 56

The effects of synthetic salmon CT, administered subcutaneously and intermittently (1 MRC U/kg/day for 15 days/month over 6 months) were investigated in 15 uremic patients on regular dialysis treatment (RDT), all presenting various degrees of osteodystrophy. Clinically, osteoarticular pain disappeared in 8 out of 10 cases; 1 patient with rib fractures had a rapid calcification of the bone fracture repair tissue. No significant changes were found in serum calcium and PTH levels. Phosphotemia showed a significant decrease within the first 20 days. The varying individual hypophosphatemic response proved to be related to the initial level of phosphatemia. The alkaline phosphatase, when increased, showed a decrease to the normal range. A significant decrease in osteoclastic hyperactivity (active resorption surface, osteoclast index) and a slight increase in osteoblastic pool (active osteoid surface) were documented. No change was noted when osteomalacia predominated. Side effects included: anorexia, nausea, vomiting, face flushing. Our data suggest that salmon CT may be usefully employed in chronic uremic patients on RDT, when secondary hyperparathyroidism predominates.
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PMID:Effect of calcitonin on bone lesions in chronic dialysis patients. 49 16

Four microgrammes of 1-alpha-hydroxycholecalciferol (1-alpha-OH D3) or 200 mug of 25-hydroxycholecalciferol (25-OH D3) were given orally every other day respectively to 10 uraemic patients (8 on chronic haemodialysis) for 1-12 weeks and to 3 patients on chronic haemodialysis for 4-8 weeks. A transilial bone biopsy and serial evaluation of serum immunoreactive PTH (iPTH) calcium phosphate and alkaline phosphatase were performed before and at the end of therapy. Both 1-alpha-OH D3 and 25-OH D3 (the latter at a 50 times higher dose) were able to depress hyperparathyroidism in two-thirds of the cases and to consistently improve the mineralisation defect. In no case did iPTH or the bone histomorphometric parameters return to normal, so that long term evaluation of these two drugs is warranted.
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PMID:1 alpha hydroxycholecalciferol and 25 hydroxycholecalciferol in renal bone disease. 93 15

Five patients with haemodialysis bone disease were treated with 1 to 1.5 mug of 1,25 (OH)2D3 daily for periods ranging from 6 -8 months. There was a significant improvement in calcium absorption but no troublesome hypercalcaemia was encountered. Secondary hyperparathyroidism improved, both histologically and radiologically, and there was a fall in serum PTH and return of serum alkaline phosphatase to within normal limits. There was also improvement in the patients' mineralisation status, but this change was slower and less marked. Muscle power improved significantly, both clinically and electromyographically.
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PMID:Long term therapy with 1,25(OH)2D3 in dialysis bone disease. 93 16

The administration of alkaline agents to a 16-year-old girl with severe renal tubular acidosis and osteomalacia caused an almost immediate rise of the urinary excretion of total hydroxyproline. The increment of the dyalizable fraction predominated over the nondyalizable component. Gradually serum phosphate and serum alkaline phosphatase increased whereas urinary calcium and magnesium and phosphate clearance declined. Serum PTH remained elevated throughout. We suggest that the correction of the metabolic acidosis might increase the transport of phosphate and calcium across the functional bone membrane leading to a rapid deposition of lime salts in the uncalcified matrix with a concomitant increase in bone collagen turnover.
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PMID:Early skeletal effect of alkali therapy upon the osteomalacia of renal tubular acidosis. 127 May 79

The investigation on several forms of uremic osteodystrophy by means of bone mineral content (BMC) measurement led to contradictory conclusions. BMC in 27 patients on periodical hemodialysis treatment was measured correlating it to the seric levels of Ca, P, Mg, alkaline phosphatase (AP), calcitonin (Ct), osteocalcin (BGP), intact parathormone (PTHi), c-terminal and mean molecule PTH. Patients on dialysis treatment from a long period of time showed high AP and low BMC levels. This correlation proved significant just for the values recorded at a third distal site of radius. Patients with BMC under the normal range showed higher BGP levels and a longer period of dialytic treatment than those presenting normal BMC. The former showed a Ct inverse correlation as to age and mineralization indexes. Higher values of Ct and BMC have been reported in males rather than in females. Hence BMC is not suited to investigate different kinds of uremic osteodystrophy. Seric PTH dosage is certainly best fitted to discriminate patients affected with hyperparathyroidism from those with low turnover osteodystrophy. BMC determination is a valid support to evaluate the bone mineral loss in patients on haemodialysis treatment. It significatively correlates to the duration of the dialytic treatment; it is higher in female than in male population; it mainly affects cortical components rather than trabecular ones and is related to a seric Ct decrease.
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PMID:[Determination of bone mineral content and correlations with calciotropic hormones in periodic hemodialysis patients]. 129 8

Parathyroid hormone degradation is intimately connected with its action. By the action of the unique renal neutral cytosolic PTH ase, PTH is split into 1-34 and 35-84 fragments, and further into 35-70 and 71-84 fragments. Amino-terminal 1-34 peptide was found to participate in the autoregulation of PTH secretion, suppressing the intact PTH secretion both in vivo in humans and in vitro in the dispersed bovine parathyroid cells. C-terminal fragment 35-84 and N-terminal fragment 1-34 both suppress the alkaline phosphatase production by ROS 17/2.8 cells to a lesser extent than the intact PTH 1-84, and the sum of the effects of the two fragments approximately equaled that of the intact hormone. Fragments 35-70 and 71-84 were devoid of such activity. Intracellular free calcium of human vascular endothelial cells was raised by intact 1-84, lowered on the contrary by C-terminal 35-84 fragment, but fragments 1-34, 35-70 and 71-84 had no effect. Fragments generated by the actions, supporting the physiological significance of PTH degradation by its target cells.
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PMID:New actions of parathyroid hormone through its degradation. 130 Mar 29

The UMR 106-06 rat osteosarcoma osteoblast-like cell line possesses calcitonin (CT) receptors in addition to expressing PTH receptors and a highly osteoblast-like phenotype, and may represent an intermediate developmental stage between early osteoblast precursors and mature osteoblasts. Therefore, we examined the effects of CT and PTH on second messenger generation and osteoblastic function in these cells. In UMR-106-06 cells, 10-1000 nM CT produced a dose-dependent stimulation of intracellular free calcium concentration ([Ca2+]i), which reached a plateau between 2-3 min. This stimulatory effect was abolished in the absence of extracellular Ca2+ ([Ca2+]o) and was mimicked by forskolin and (Bu)2cAMP. One hundred nanomolar CT also produced a slight but significant increase in inositol triphosphate production (13%, P less than 0.05) but did not produce a rapid, transient increase in [Ca2+]i. In contrast, PTH produced a rapid, transient increase in [Ca2+]i, which reached a maximum within 30 sec. This stimulatory effect of PTH on [Ca2+]i signal was dose-dependent and accompanied by a parallel stimulation of inositol triphosphate production. PTH, forskolin, and (Bu)2cAMP all produced a marked dose-related suppression of both DNA and collagen synthesis, which paralleled their stimulatory effects on intracellular cAMP levels. In marked contrast, CT only minimally reduced DNA and collagen synthesis despite producing comparable increases in intracellular cAMP. One hundred nanomolar CT also stimulated alkaline phosphatase specific activity by 33% (P less than 0.05). Thus, CT stimulates cAMP, [Ca2+]i, and inositol phosphate second messengers in UMR 106-06 cells. However, in contrast to other agents which elevate intracellular cAMP levels, CT does not suppress DNA synthesis. These results suggest that the linkage of CT receptor second messengers to effects on cell function differ from those of PTH and/or that CT may produce additional second messenger(s) which antagonize the antiproliferative effect of increased cAMP levels in UMR-106-06 cells.
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PMID:Effects of calcitonin on 3',5'-cyclic adenosine monophosphate and calcium second messenger generation and osteoblast function in UMR 106-06 osteoblast-like cells. 130 38


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