Biomedical Engineering Reference
In-Depth Information
Fig. 3.
Expression of
I
K,Ach
and
I
K,ATP
ion channel subunits in CMG cells.
a
The CMG cells
expressed both GIRK1 and GIRK2B at 6 weeks. They did not express GIRK4.
b
Kir6.2 and
SUR2A were expressed in CMG cells from 4 weeks after Differentiation.
differentiation, and that HCN4 and HCN2 was expressed from 2 to 6 weeks, respec-
tively (Fig. 4a). These patterns of HCN channel expression in differentiated CMG cells
were consistent with the developmental changes of normal cardiomyocytes.
The L-type Ca
2+
channel in cardiomyocytes is composed of 1 Į1,
ȕ
and Į2Ȗ sub-
units. RT-PCR demonstrated that the Į 1 subunit of the cardiac L-type Ca
2+
channel
(Ca
v
1.2) was not expressed before CMG cell differentiation, but was expressed from
2 weeks (Fig. 4b), consistent with the finding of the action potential in differentiated
cardiomyocytes.
We next examined whether the regenerated cardiomyocytes expressed functionally
active cardiac L-type Ca
2+
channels. Cardiac L-type Ca
2+
channels are sensitive to the
Ca
2+
channel blocker verapamil. We recorded action potentials from the bone marrow-
derived cardiomyocytes, added verapamil into the conditioned media, and observed
