First published online April 8, 2004
Journal of Experimental Biology 207, 1665-1674 (2004)
Published by The Company of Biologists 2004
doi: 10.1242/jeb.00925
Cadmium induces both pyruvate kinase and Na+/H+ exchanger activity through protein kinase C mediated signal transduction, in isolated digestive gland cells of Mytilus galloprovincialis (L.)
Stefanos Dailianis and
Martha Kaloyianni*
Laboratory of Animal Physiology, Zoology Department, School of Biology,
Faculty of Science, Aristotle University of Thessaloniki 54124, Greece
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Fig. 1. The effect of different concentrations of cadmium on intracellular pH (pHi)
of isolated digestive gland cells of Mytilus galloprovincialis.
Values are means ± S.D. of at least 7 independent
experiments. In each experiment, the tissue of four animals was used.
*Significantly different after cadmium treatment from control value
at the respective time point. Values that share the same letter (a, b) are
statistically significant different from each other at the same time point;
Dunnet's test, P<0.01.
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Fig. 2. Effect of cadmium and various effectors on Na+ influx (µmol
Na+ h–1 10–6 cells) in isolated
digestive gland cells of Mytilus galloprovincialis. Cells were
treated for 30 min either with cadmium at 50 µmol l–1 or
cadmium (50 µmol l–1) + 20 nmol l–1 EIPA
(a selective inhibitor of Na+/H+ exchanger), or cadmium
(50 µmol l–1) + 20 nmol l–1 calphostin C
(a specific inhibitor of protein kinase C), or cadmium (50 µmol
l–1) + 10 µmol l–1 propranolol (a
ß-adrenergic antagonist). See Materials and methods for details. Values
are means ± S.D. of at least 4 independent
experiments. In each experiment, the tissue of four animals was used.
*Significant difference between control value and that observed
after metal treatment;  significant difference between the
value obtained after cadmium treatment with that obtained after cadmium +
effector treatment; Dunnet's test, P<0.01.
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Fig. 3. The effect of cadmium (50 µmol l–1) and/or various
effectors on pHi of isolated digestive gland cells of Mytilus
galloprovincialis. Cells were treated with PMA, a potent activator of
protein kinase C, alone (10 nmol l–1) or cadmium (50 µmol
l–1) alone, or + 20 nmol l–1 calphostin C (a
specific inhibitor of protein kinase C). The results are mean ±
S.D. of at least 7 independent experiments. In each
experiment, the tissue of four animals was used. *Significant
difference between the values obtained after treatment of the cells with PMA
or with cadmium and the control value at the respective time point; Dunnet's
test, P<0.01.
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Fig. 4. Effect of cadmium alone and cadmium + Na+/H+
exchanger inhibitors on PK activity of isolated digestive gland cells of
Mytilus galloprovincialis. 100% represents enzyme activity in the
absence of cadmium (5.23±1.04 nmol min–1
mg–1 protein). Cells were treated for 30 min either with 50
µmol l–1 of cadmium alone, or 50 µmol
l–1 cadmium + 10 µmol l–1 amiloride (an
inhibitor of most plasma membrane Na+ transport systems) or + 20
nmol l–1 EIPA (a selective inhibitor of
Na+/H+ exchanger). PK activity in the presence of 20
nmol l–1 EIPA alone after 30 min of incubation was found to
be 5.38±0.7 nmol min–1 mg–1 protein.
The results (expressed as % PK activity of control value) are mean ±
S.D. of at least 7 independent experiments. In each
experiment, the tissue from four animals was used. *Significant
difference between the value after cadmium treatment and the control value;
significant difference between the values after cadmium
treatment with those observed after cadmium + inhibitors; Dunnet's test,
P<0.01.
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© The Company of Biologists Ltd 2004
