Calcium mobilization

Although it is being found that vitamin D metaboUtes play a role ia many different biological functions, metaboHsm primarily occurs to maintain the calcium homeostasis of the body. When calcium semm levels fall below the normal range, 1 a,25-dihydroxy-vitainin is made when calcium levels are at or above this level, 24,25-dihydroxycholecalciferol is made, and 1 a-hydroxylase activity is discontiaued. The calcium homeostasis mechanism iavolves a hypocalcemic stimulus, which iaduces the secretion of parathyroid hormone. This causes phosphate diuresis ia the kidney, which stimulates the 1 a-hydroxylase activity and causes the hydroxylation of 25-hydroxy-vitamin D to 1 a,25-dihydroxycholecalciferol. Parathyroid hormone and 1,25-dihydroxycholecalciferol act at the bone site cooperatively to stimulate calcium mobilization from the bone (see Hormones). Calcium blood levels are also iafluenced by the effects of the metaboUte on intestinal absorption and renal resorption. 

Several other techniques for have evolved for biochemical assays. In chapter 2 of this book, Omann and Sklar report on a method of fluoroimmunoassay where the bound and unbound antigen are separated by the quenching of fluorescence that accompanies antibody binding. Then, in chapter 3, Holl and Webb show how they achieved a sensitive measurement of nucleic acids by the enhancement in fluorescence that accompanies the binding of fluorescent dyes to nucleic acids. Chandler et al, also used fluorescence enhancement to monitor calcium mobility in neutrophil cells. 

Stimulating activation of vitamin D by 1-a-hydroxylase to cal-citriol (1,25-dihydroxyvitmin D3) to promote calcium absorption in the GI tract and increased calcium mobilization from bone... 

In contrast, functional assays that look at post-receptor events, such as cAMP stimulation (Gs), cAMP inhibition (G ), inositol triphosphate (IP3)/mono-phosphate (IP1) increase (Gq), or intracellular calcium mobilization (Gq), are homogeneous, for the most part nonradioactive, and easy to automate (with... 

Fig. 3. Comparison between IP-One kit versus calcium mobilization assay (384-well format). Human embryonic kidney (HEK) 293 cells expressing a chemokine receptor were evaluated on HTRF IP-One kit (CisBio, Bedford, MA) and fluroescent imaging plate reader (FLIPR) with Calcium 3 kit (Molecular Devices, Mountain View, CA).

Rail, T. W., Evolution of the mechanism of action of methylxanthines From calcium mobilizers to antagonists of adenosine receptors, Pharmacologist, 24, 277, 1982. 

SK Joseph, JR Williamson. (1983). The origin, quantitation, and kinetics of intracellular calcium mobilization by vasopressin and phenylephrine in hepatocytes. J Biol Chem 258 10425-10432. 

Histamine acts on four G-protein-coupled receptors, three of which are clearly important in the brain 256 H, receptors are intronless GPCRs linked to Gq and calcium mobilization 256... 

Gardner, C.R., Laskin, J.D., and Laskin, D.L., Platelet-activating factor-induced calcium mobilization and oxidative metabolism in hepatic macrophages and endothelial cells, J. Leukoc. Biol., 53, 190, 1993. 

Alteration of membrane structure in immune cells by PUFAs can lead to defective signal transduction and decreased function. PUFA treatment of CD3-activated human T cells results in decreased calcium mobilization, proliferation and IL-2 production... 

Quinolinyl compounds were first reported by Chan et al. as potent orexin receptor antagonists with excellent selectivity for OX1, good brain permeability and in vivo activity following i.p. dosing [62,63]. In fact, compounds SB-334867 (21), SB-408124 (22) and SB-410220 (23) displayed high affinity for the OX1 receptor in both whole cell (Ki — 99, 57 and 19nM, respectively) and membrane formats (X = 38, 27 and 4.5 nM, respectively). Meanwhile, native orexin peptides A and B display affinities for the OX1 receptor with K values of 318 and 1516 nM, respectively. In addition, calcium mobilization studies showed that all three are functional antagonists of the OX1 receptor, with potencies in line with their affinities, and with 50-fold... 

When cyanide blocks oxidative metabolism in mitochondria, cells shift their metabolism and enhanced glucose utilization occurs. One consequence of this altered metabolic pattern is accumulation of nicotinamide adenine dinucleotide (NADH). NADH is a powerful stimulant of calcium mobilization from cell stores through "inositol triphosphate receptors." Elevated calcium damages cells. Increase in cellular NADH, therefore, is an important event in the toxic action of cyanide (Kaplin et al. 1996). 

Merritt, J. E., Moores, K. E. (1991). Human neutrophils have a novel purinergic P2-type receptor linked to calcium mobilization. Cell. Signalling 3,243-9. 

Three hormones are secreted by the thyroid thyroxine (T4) and tri-iodothyronine (T3) are usually referred to as the thyroid hormones and calcitonin, a peptide, which under certain circumstances, affects calcium mobilization and is secreted from specialized so-called C cells. Only T3 and T4 will be discussed further at this point. 

J. T. Ransom, D. L. DiGiusto, and J. Cambier, Flow cytometric analysis of intracellular calcium mobilization, Methods Enzymol. 141, 53-63(1987). 

G. L. Rossi, D. J. Young, S. I. Wasserman, and K. E. Barrett, Calcium mobilization in activated mast cells monitored by flow cytometric analysis. Agents Actions 31, 257-262 (1990). 

Huang, W-C. and Chueh, S-H., 1996, Calcium mobilization from the intracellular... 

Melendez, A., Floto, R.A., Gillooly, D.J., Harriett, M.M and Allen, J.M., 1998, FcyRI coupling to phospholipase D initiates sphingosine kinase-mediated calcium mobilization and vesicular trafficking, J. Biol. Chem. 273 9393-9402. 

Orlati, S., Hreha, S. and Rugolo, M., 1997, Pertussis toxin- and PMA-insensitive calcium mobilization by sphingosine in CFPAC-1 cehs Evidence for aphosphatidic acid-dependent mechanism, Biochim. Biophys. Acta 1358 93-102. 

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