Cell lines derived from embryonic tissue of
Drosophila
melanogaster are used increasingly for expression
and co-expression of cloned
Drosophila
membrane receptors and ion channels. In this study
we applied CCD imaging techniques in conjunction
with dyes sensitive to Ca
2+ (Fura-2/AM), pH
(BCECF/AM) and Cl
- (MQAE, SPQ) to the following
Drosophila cell lines: monoclonal Kc cells;
monoclonal S2 cells; 8 clonal cell lines of nervous
system origin. Resting [Ca
2+]
i levels in the range
20—70 nM were detected in S2 cells and in all the
neural cell lines. All the cell lines failed to show
[Ca
2+]
i responses to high K
+ (50 mM). Also ineffective
were the neurotransmitters/neuromodulators:
dopamine (100 μM), GABA (100 μM), muscimol
(10 μM), histamine (100 μM), 5-HT (100 μM), epinephrine
(100 μM), octopamine (100 μM), ATP
(100 μM) and acetylcholine (100 μM). S2 cells did
respond to the addition in Ca
2+ -free medium (1 mM
EGTA) of 4—10 μM ionomycin and to 1 μM thapsigargin.
Monensin (10 μM), a Na
+/H
+ ionophore, also
resulted in a rise in [Ca
2+]
i. Thapsigargin (1 μM)
failed to affect pH
i. Depletion of an InsP
3-sensitive
intracellular Ca
2+ store by thapsigargin (1 μM)
evoked activation of endogenous, depletion-operated
Ca
2+ entry which was blocked by the Gd
3+
(1—10 μM).
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