Calcium ionophores

Calcium ionophore I (ETH 1001) [58801-34-6] M 685.0. This is a neutral Ca selectophore. It can be purified by thick layer (2mm) chromatography (Kieselgel F245) and eluted with Me2CO-CHCl3 (2 1). [Helv Chim Acta 56 1780 1 973.]... 

As expected, ionomycin, a calcium ionophore, causes a sustained rise in the free intracellular concentration to approximately 450 nM (Figure 4). In this system, pardaxin induced an increase in intracellular [Ca ] only in the presence of extracellular Ca (Figure 4). These results indicate that pardaxin mediated a Ca influx but did not release Ca from intracellular stores. This influx is most probably mediated directly by pardaxin channels and possibly also indirectly by activation of the Ca channels of the chromaffin cells by the depolarization produced by the pardaxin channels (data not shown). These observations further substantiate our hypothesis 10) that transmembrane fluxes of Na and Ca are involved in the pathological action of pardaxin. 

Values are presented as mU/min/mg and mean (SEM) of 4-6 muscles. Muscles were either Incubated without any further treatment, stimulated for 30 min with repetitive tetanii or treated with the calcium ionophore (A23187 - 20 /im) for 30 min. Data presented represent efflux over 90-120 min post-treatment. Animals were fed either a vitamin E-deficient or vitamin E-supplemented diet (Phoenix et al., 1990) for 6 weeks prior to study. Data derived from O Farrell (1994). 

Johnson, K., Sutcliffe, L., Edwards, RH.T. and Jackson, M.J. (1988). Calcium ionophore enhances the electron spin resonance signal from isolated skeletal muscle. Bitxhim. Biophys. Acta 964, 285-288. 

Br > Cl > I. This conductance was not time-dependent. On the other hand, Cl conductance stimulated by the Ca2+ ionophore A23187 (2.5 pM) or elevation in the free Ca2+ levels in the pipet from 100 to 500 nM was time-dependent and exhibited a nonlinear current-voltage relationship that was outwardly rectifying. The permselectivity of this Ca2+-stimulated conductance was 1 > Br > cr, distinguishing it from the cAMP-stimulated Cfr conductance. As both calcium ionophore A23187 and cAMP were shown to elevate the Cl conductance of the cornea, it is quite likely that these two types of Cr channels are present in the corneal epithelium [96,106,114],... 

KS Kan, R Coleman. (1988). The calcium ionophore A23187 increases the tight-junctional permeability in rat liver. Biochem J 256 1039-1041. 

In Fig. 9.4, the results are shown of an experiment using a double (annexinA4-EYFP+ annexinA4-mCherry) transfected cell immediately after addition of the calcium ionophore ionomycin (top) and 5 min after application of ionomycin (bottom). Clearly visible is the diffuse localization of annexin A4 before relocation and the more structured localization (into membrane ruffles and filopodia) after relocation. More importantly, the EYFP fluorescence lifetime is quenched from 2.9 ns before translocation to... 

MF effects on FA relatives and healthy donors. (Fanconi anemia is an autosomal recessive disease associated with the overproduction of free radicals, Chapter 31.) It has been shown earlier [215] that FA leukocytes produce the enhanced amount of hydroxyl or hydroxyl-like free radicals, which are probably formed by the Fenton reaction. It was suggested that MF would be able to accelerate hydroxyl radical production by FA leukocytes. Indeed, we found that MF significantly enhanced luminol-amplified CL produced by non-stimulated and PMA-stimulated FA leukocytes but did not affect at all oxygen radical production by leukocytes from FA relatives and healthy donors (Table 21.3). It is interesting that MF did not also affect the calcium ionophore A23187-stimulated CL by FA leukocytes, indicating the absence of the calcium-mediated mechanism of MF activity, at least for FA leukocytes. 

Interestingly, pretreatment of isolated rat peritoneal mast cells with NT desensitizes the cells to the subsequent stimulation by compound 48/80 (Figure 4.3). However, the desensitized cells are still responsive to stimulation by the calcium ionophore, A23187, in the presence of Ca (Figure 4.3). A similar observation has been made when compound 48/80 and the peptides,... 

Stimulation by thrombin does not lead to the generation of leukotriene C4 or B4, whereas stimulation of the same mast cells by the calcium ionophore, A23187, does. The secretory response elicited by thrombin is prevented by preincubation with AT-III, a plasma inhibitor of thrombin, or by hirudin, a thrombin inhibitor derived from the leech [135],... 

Dahlgren, C. (1987). Difference in extracellular radical release after chemotactic factor and calcium ionophore activation of the oxygen radical-generating system in human neutrophils. Biochim. Biophys. Acta 930, 33-8. 

In polymorphonuclear leucocytes (PMNL, neutrophils), secretory responses measured as vitamin B -binding protein release were inhibited by feverfew extract when the response was induced by the chemotactic peptide FMLP or arachidonic acid but not when the calcium ionophore A23187 was... 

Howard, T. H. and Wang, D. (1987) Calcium ionophore, phorbol ester and chemotactic peptide-induced cytoskeleton reorganization in human neutrophils. J. Clin. Invest. 79,1359-1364. 

The histamine- and leukotriene B4-releasing potential of the RCBPA P743 has been investigated in vitro on the RBL-2H3 mast cell line [25]. RBL-2H3 cells (with permission of Dr RP Siraganian, National Institutes of Health, Bethesda, MD, USA) were replated on Eagle s minimum essential medium and incubated for 30 minutes at 37 °C in 5% CO2 with the test-solutions. Calcium ionophore A23187 was used as a positive control. The viability of mast cells was determined by means of a quantitative colorimetric assay that is based on the abiUty of viable cells to cleave the reagent MTT [33]. 

In contrast to the reports by Wang et al. (1997) and Grant et al. (1994), (see page 28) it was also reported that H-7 and staurosporine blocked apoptosis following induction by ara-C in HL-60 cells (Kharbanda, et al, 1991). The calcium ionophore A23187 induced apoptosis in immature mouse thymocytes. H-7 inhibited the DNA fragmentation and cell death (Kizaki et al.. 

A23187 <2> (<2> calcium ionophore, 216% activation of ceramide kinase in A549 lung adenocarcinoma cells [6]) [6]... 

Pettus, B.J. Bielawska, A. Spiegel, S. Roddy, P. Hannun, Y.A. Chalfant, C.E. Ceramide kinase mediates cytokine- and calcium ionophore-induced arachi-donic acid release. J. Biol. Chem., 278, 38206-38213 (2003)... 

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