N. Ullrich et H. Sontheimer, BIOPHYSICAL AND PHARMACOLOGICAL CHARACTERIZATION OF CHLORIDE CURRENTSIN HUMAN ASTROCYTOMA-CELLS, American journal of physiology. Cell physiology, 39(5), 1996, pp. 1511-1521
Expression of voltage-activated ion channels was studied in primary cu
ltures from seven freshly resected human primary brain tumors and in a
n established human astrocytoma cell line, STTG1. Astrocytoma cells co
nsistently expressed voltage-dependent outwardly rectifying currents.
Currents activated at potentials >45 mV and showed outward transients
on termination of voltage steps. Currents reversed at the Cl- equilibr
ium potential, suggesting that they were largely carried by Cl-. Alter
ing extracellular K+ or Na+ concentration did not alter currents; neit
her did replacement of intracellular K+ by Cs+ or intracellular Na+ by
N-methyl-D-glucosamine. Anion-substitution experiments suggest the fo
llowing permeability sequence, determined from shifts in tail current
reversal potential: I- > NO3- > Br- > Cl- > acetate > isethionate > F-
> glutamate. Currents were sensitive to the Cl- channel blockers chlo
rotoxin, 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS), and
4,4'-dinitrostilbene-2,2'disulfonic acid (DNDS), with chlorotoxin bein
g most effective, yielding >80% block at 590 nM. DIDS (100 mu M) and D
NDS (100 mu M) reduced currents by 33.5 and 38.2%, respectively. Curre
nts were also sensitive to Zn2+ (100 mu M, 47% block) and Cd2+ (25 mu
M, 42% block). Reducing extracellular Ca2+ concentration decreased out
ward currents by 58% and almost completely eliminated transients, sugg
esting that Cl- currents are Ca2+ dependent. Cl- channel block resulte
d in altered cell proliferation as determined by [H-3]thymidine incorp
oration, suggesting that these channels may be involved in astrocytoma
growth control.