The effect of boromycin on the Ca2+ homeostasis |
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Authors: | Lakatoš B Kaiserová K Orlický J Knézl V Varečka L' |
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Institution: | Department of Biochemistry and Microbiology, Slovak University of Technology, Bratislava, Slovak Republic. |
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Abstract: | A boron-containing antibiotic, boromycin (BM), was found to influence the Ca2+ homeostasis in both excitable and non-excitable cells. In non-excitable cells (human erythrocytes and leucocytes) it inhibited the resting passive45Ca2+ transport in 10–6–10–5 mol/L concentrations. In human erythrocytes, the passive 45Ca2+ transport induced by the presence of 1 mmol/L NaVO3 was inhibited by boromycin (90% inhibition) as well. The inhibitory effect of BM on the NaVO3-induced passive 45Ca2+ transport was diminished in the presence of inhibitory concentrations of nifedipine (10 mol/L – 60% inhibition) or of those of K+
o (75 mmol/L – 20% inhibition). On the other hand, in rat brain synaptosomes, and rat cardiomyocytes, BM stimulated the passive 45Ca2+ transport in resting cells at similar concentrations. In rat cardiomyocytes the stimulation was transient. The stimulatory effect on the passive 45Ca2+ transport in rat brain synaptosomes was accompanied with the increase of cytoplasmic Ca2+ concentration measured by means of the entrapped fluorescent Ca2+ chelator fura-2. The stimulatory effect of BM was diminished when synaptosomes were pre-treated with veratridine (10 mol/L) which itself stimulated the passive 45Ca2+ transport. At saturating concentrations of veratridine, no stimulatory effect of BM was observed. These results could be explained by the indirect interaction of BM with both Ca2+ and Na+ transport systems via transmembrane ionic gradients of monovalent cations and could be useful in determining whether the cells belong to excitable, or non-excitable cells. |
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Keywords: | human red blood cells Ca2+ influx ATP depletion vanadate Ca2+ activated K+ channel Gá rdos effect |
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