Li+ Influx and Binding, and Li+/Mg2+ Competition in Bovine Chromaffin Cell Suspensions as Studied by 7Li NMR and Fluorescence Spectroscopy
Open Access
- 1 January 2000
- journal article
- research article
- Published by Wiley in Metal-Based Drugs
- Vol. 7 (6) , 357-364
- https://doi.org/10.1155/mbd.2000.357
Abstract
Li+ influx by bovine chromaffin cells, obtained from bovine adrenal medulla, was studied in intact cell suspensions using 7Li NMR spectroscopy with the shift reagent [Tm(HDOTP)]4-. The influx rate constants, ki, were determined in the absence and in the presence of two Na+ membrane transport inhibitors. The values obtained indicate that both voltage sensitive Na+ channels and (Na+/K+)‐ATPase play an important role in Li+ uptake by these cells. 7Li NMR T1 and T2 relaxation times for intracellular Li+ in bovine chromaffin cells provided a T1/T2 ratio of 305, showing that Li+ is highly, immobilized due to strong binding to intracellular structures. Using fluorescence spectroscopy and the Mg2+ fluorescent probe, furaptra, the free intracellular Mg2+ concentration in the bovine chromaffin cells incubated with 15 mM LiCl was found to increase by about mM after the intracellular Li+ concentration reached a steady state. Therefore, once inside the cell, Li+ is able to displace Mg2+ from its binding sites.Keywords
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