Li+ influx and binding, and Li+/Mg2+ competition in bovine chromaffin cell suspensions as studied by Li NMR and fluorescence spectroscopy

Carla P. Fonseca, Liliana P. Montezinho, Graça Baltazar, Brian Layden, Duarte M. Freitas, Carlos F G C Geraldes, M. Margarida C A Castro

Research output: Contribution to journalArticlepeer-review

5 Scopus citations

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 15mM LiCl was found to increase by about 1mM after the intracellular Li+ concentration reached a steady state. Therefore, once inside the cell, Li+ is able to displace Mg2+ from its binding sites.

Original languageEnglish (US)
Pages (from-to)357-364
Number of pages8
JournalMetal-Based Drugs
Volume7
Issue number6
DOIs
StatePublished - 2000

ASJC Scopus subject areas

  • Toxicology
  • Pharmacology
  • Drug Discovery
  • Inorganic Chemistry

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