Li influx and binding, and li/mg competition in bovine chromaffin cell suspensions as studied by li NMR and fluorescence spectroscopy |
| |
Authors: | Fonseca C P Montezinho L P Baltazar G Layden B Freitas D M Geraldes C F Castro M M |
| |
Affiliation: | Department of Biochemistry University of Coimbra P.O. Box 3126 Coimbra 3000 Portugal. |
| |
Abstract: | Li(+) influx by bovine chromaffin cells, obtained from bovine adrenal medulla, was studied in intact cell suspensions using (7)Li NMR spectroscopy with the shift reagent [Tm(HDOTP)](4-). The influx rate constants, k(i), 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. (7)Li NMR T(1) and T(2) relaxation times for intracellular Li(+) in bovine chromaffin cells provided a T(1)/T(2) ratio of 305, showing that Li(+) is highly, immobilized due to strong binding to intracellular structures. Using fluorescence spectroscopy and the Mg(2+) fluorescent probe, furaptra, the free intracellular Mg(2+) 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 Mg(2+) from its binding sites. |
| |
Keywords: | |
本文献已被 PubMed 等数据库收录! |
|