The effect of boromycin on the Ca2+ homeostasis.
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 passive 45Ca2+ transport in 10(-6)-10(-5) mol/L concentrations. In human erythrocytes, the passive 15Ca2+ 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 micromol/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 micromol/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.
Lakatos
B
B
Department of Biochemistry and Microbiology, Slovak University of Technology, Bratislava, Slovak Republic.
Kaiserová
K
K
Simkovic
M
M
Orlický
J
J
Knézl
V
V
Varecka
L
L
D000818:Animals; D001881:Borates / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004912:Erythrocytes / Q000187:drug effects / Q000378:metabolism; D005260:Female; D006321:Heart / Q000187:drug effects; D006706:Homeostasis / Q000187:drug effects*; D006801:Humans; D007962:Leukocytes / Q000187:drug effects / Q000378:metabolism; D008297:Male; D051381:Rats; D013574:Synaptosomes / Q000187:drug effects
D001881:Borates; C000302:boromycin; D002118:Calcium