Calcium efflux

Gitelzon, G. I., Tugai, V. A., and Zakharchenko, A. N. (1990). Production of obelin, a calcium-activated photoprotein, from Obelia longissima and its application for registration of the calcium efflux from the fragmented sarcoplasmic reticulum of skeletal muscles. Ukr. Biokhim. Zh. 62 69-76. 

BAL—see Propan-l-ol, 2,3-dimercapto-Bacillus cereus calcium transport, 6,572 Bacillus megaterium calcium efflux, 6, 570 calcium transport, 6,572 sporulation zinc transport, 6, 572 Bacillus spp. sodium ions, 6, 559 sporulation... 

If some of the electrophysiological effects of oxidant stress occur secondary to an elevation in intracellular calcium, it is important to consider the possible factors that may underlie the initial elevation of calcium. In the simplest analysis, elevation of cytosolic calcium may be due to (1) redistribution of intracellular calcium stores (2) increased calcium influx or (3) decreased calcium efflux. 

While our data using this technique are still preliminary, we have observed that 25 yU/ml insulin inhibits the rate of calcium efflux from renal slices (28). This effect of insulin was gradually reduced at the higher concentrations of insulin. The effects of insulin on calcium exchange appear to be localized in the mitochondrial compartment. Further work is needed to determine whether insulin affects specific enzyme systems which are known to play a role in renal calcium transport, and which cellular or subcellular compartments are involved. This would substantially increase our understanding of the regulation of urinary calcium excretion, and of ways in which excessive loss of calcium by this route might be avoided. 

Vj = rate of calcium influx Ve = rate of calcium efflux L = solubility product of calcium oxalate. 

The contribution of the lipids to the low permeability of the sarcoplasmic vesicles for calcium is revealed by the tremendous increase in the rate of calcium efflux which occurs when the lipid phase is modified. The following modifications proved to be effective treatment of the sarcoplasmic reticulum vesicles with low concentrations of ether156, splitting of a small fraction of the phospholipids by phospholipase A2... 

The affinities of the transport protein for the nucleoside triphosphates ITP and GTP and the corresponding diphosphates deduced from the concentration dependence of either calcium-dependent phosphate liberation or phosphate incorporation during calcium efflux are at least 10 to 400 times lower than the affinity of the adenine nucleotides (Fig. 12). The affinities for acetyl phosphate, carbamyl phosphate, para-nitro-... 

Microbial cells maintain low internal [Ca2+] levels through the operation of several types of highly active and specific efflux processes.180,184 Efflux of Ca2+ can only be studied with difficulty in whole cells, partly because of complications resulting from the binding of Ca2+ to the cell walls. Nevertheless, the presence of active mechanisms for the efflux of calcium are shown by the fact that extreme temperatures or inhibitors result in increased levels of intracellular calcium. Efflux of Ca2+ has been demonstrated for B. megaterium, while ATP-linked efflux of Ca2+ has been demonstrated for Streptococcus faecalis.lss... 

Wolde Mussie, E., Vande Waa, J., Pax, R.A., Fetterer, R. and Bennett, J.L. (1982) Schistosoma mansoni calcium efflux and effects of calcium-free media on responses of the adult male musculature to praziquantel and other agents inducing contraction. Experimental Parasitology 53, 270-278. 

Wasaki, S., Sakaida, I., Uchida, K., Kimura, T., Kayano, K., and Okita, K., 1997, Preventive effect of cyclosporin A on experimentally induced acute liver injury in rats, Liver 17, pp. 107-114 Weiss, J.N., Korge, P., Honda, H. M., and Ping, P., 2003, Role of the mitochondrial permeability transition in myocardial disease, Circ. Res 93, pp. 292-301 Wingrove, D.E. and Gunter, T. E., 1986a, Kinetics of mitochondrial calcium transport. I. Characteristics of the sodium-independent calcium efflux mechanism of liver mitochondria, J. Biol. Chem. 261, pp.15159-15165... 

Gay CV, Lloyd QP. 1995. Characterization of calcium efflux by osteoblasts derived from long bone periosteum. Comp Biochem Physiol A Physiol. Ill 257-61. 

The SR membrane contains a very efficient calcium uptake transporter, which maintains free cytoplasmic calcium at very low levels during diastole by pumping calcium into the SR. The amount of calcium sequestered in the SR is thus determined, in part, by the amount accessible to this transporter. This in turn is dependent on the balance of calcium influx (primarily through the voltage-gated membrane calcium channels) and calcium efflux, the amount removed from the cell (primarily via the sodium-calcium exchanger, a transporter in the cell membrane). 

Mutants Calcium Efflux Cj0 (Thrombin, nM) Calcium Efflux EC50 (SFLLRNP-NHz ]iM)... 

The effects of the mutations on functional responses were determined on thrombin receptors that were expressed in Xenopus oocytes. Agonist-stimulated calcium efflux with human a-thrombin (10 nM) and SFLLRNP-NH2 (40 pM), as described previously,29 was employed to determine the functional responsiveness of the receptor. 

Adey, W. R. Bawin, S. M. Lin-Liu, S. Increased calcium efflux from cerebral tissue exposed to weak modulated microwave fields. Physiological Society, London, July 1980. Proceedings, 23P. 

Lin-Liu, S. Adey, W. R. Effect of ELF-modulated A50 MHz field on calcium efflux from rat synaptosomes. Bioelectromagnetics Society, Second Annual Meeting, San Antonio, September 1980. Bioelectromagnetics 1980, 1(2), 211 (abstract). 

The respiratory activity of the brain tissue was determined by measuring the rate of oxygen uptake with a Clark oxygen electrode (7). The sample of tissue (a brain half) was treated exactly as if used in a calcium efflux experiment except no radioactivity or RF power was used. Following this procedure which required about 55 minutes, the tissue was placed in the oxygen electrode cell containing 1.6 ml of the standard medium (pH 7.8) at 37°C and the rate of oxygen uptake was recorded. 

Proposed Mechanism Responsible for Calcium Efflux. Calcium-ion efflux from brain tissue does not appear to be a function of carrier frequency, since equivalent results are obtained at carrier frequencies of 50, 147, and 450 MHz provided the internal electric field intensity is the same in each brain. However, an important question remains why should there be alternate ranges, or windows, of internal electric field intensity which cause efflux enhancement An hypothesis that is consistent with and helps explain this finding is ... 

Effect of Buffer Solution. An essential component of the medium in potentiating enhanced calcium-ion efflux due to RF radiation appears to be bicarbonate. We have substituted both Tris and- HEPES buffers for bicarbonate and have failed to observe enhanced calcium efflux at 0.83 mW/cm2 (147 MHz). The same result has been reported by Bawin (personal communication) when bicarbonate was replaced by imidazole or MOPS buffers. Although the significance of this finding is not yet apparent, these results should be of interest to other investigators who attempt to replicate or extend the studies on RF-induced calcium-ion efflux from brain tissue. One should also note that the initial report by Bawin et al. (1) incorrectly listed the bicarbonate concentration at 24 mM instead of 2.4 mM (22). 

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