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Inhibitory effect of 2,3‐butanedione monoxime (BDM) on Na + /Ca 2+ exchange current in guinea‐pig cardiac ventricular myocytes
The effect of 2,3‐butanedione monoxime (BDM), a ‘chemical phosphatase’, on Na + /Ca 2+ exchange current ( I NCX ) was investigated using the whole‐cell voltage‐clamp technique in single guinea‐pig cardiac ventricular myocytes and in CCL39 fibroblast cells expressing canine NCX1. I NCX was identified...
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| Published in: | British journal of pharmacology 2009-01, Vol.132 (6), p.1317-1325 |
|---|---|
| Main Authors: | , , , , , , , |
| Format: | Article |
| Language: | English |
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| Online Access: | Get full text |
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| Summary: | The effect of 2,3‐butanedione monoxime (BDM), a ‘chemical phosphatase’, on Na
+
/Ca
2+
exchange current (
I
NCX
) was investigated using the whole‐cell voltage‐clamp technique in single guinea‐pig cardiac ventricular myocytes and in CCL39 fibroblast cells expressing canine NCX1.
I
NCX
was identified as a current sensitive to KB‐R7943, a relatively selective NCX inhibitor, at 140 m
M
Na
+
and 2 m
M
Ca
2+
in the external solution and 20 m
M
Na
+
and 433 n
M
free Ca
2+
in the pipette solution.
In guinea‐pig ventricular cells, BDM inhibited
I
NCX
in a concentration‐dependent manner. The IC
50
value was 2.4 m
M
with a Hill coefficients of 1. The average time for 50% inhibition by 10 m
M
BDM was 124±31 s (
n
=5).
The effect of BDM was not affected by 1 μ
M
okadaic acid in the pipette solution, indicating that the inhibition was not
via
activation of okadaic acid‐sensitive protein phosphatases.
Intracellular trypsin treatment
via
the pipette solution significantly suppressed the inhibitory effect of BDM, implicating an intracellular site of action of BDM.
PAM (pralidoxime), another oxime compound, also inhibited
I
NCX
in a manner similar to BDM.
Isoprenaline at 50 μ
M
and phorbol 12‐myristate 13‐acetate (PMA) at 8 μ
M
did not reverse the inhibition of
I
NCX
by BDM.
BDM inhibited
I
NCX
in CCL39 cells expressing NCX1 and in its mutant in which its three major phosphorylatable serine residues were replaced with alanines.
We conclude that BDM inhibits
I
NCX
but the mechanism of inhibition is not by dephosphorylation of the Na
+
/Ca
2+
exchanger as a ‘chemical phosphatase’.
British Journal of Pharmacology
(2001)
132
, 1317–1325; doi:
10.1038/sj.bjp.0703926 |
|---|---|
| ISSN: | 0007-1188 1476-5381 |
| DOI: | 10.1038/sj.bjp.0703926 |