Biomedical Engineering Reference
In-Depth Information
(-4.68 and -9.3 pA/pF) [6, 8]. In rat NCMs,
I
K1
current densities between - 7
and - 9 pA/pF at -100 mV have been reported [5, 7]. HEK-KWGF cells had a
mean membrane potential of - 75.2 ± 0.5 mV (N = 20). No
I
K1
was found in
non-transfected HEK- 293 cells.
3.2 Co-culture of HEK-KWGF Cells with NCMs
Neonatal rat cardiomyocytes share several features with nodal cardiomyocytes,
of which their automaticity is the most characteristic. Furthermore, they display
a maximal diastolic membrane potential of -65 mV and a prominent phase 4
depolarization. As
I
K1
is the main determinant of the RMP, we compared
RMP of NCM clusters with that of NCM/HEK-KWGF cell clusters. NCM
clusters displayed a maximal diastolic membrane potential of -65.1 ± 2.8 mV
(N = 4), which significantly decreased to -77.6 ± 3.4 mV (N = 6) (p < 0.01;
Student's
t
-test) in NCMs coupled to one or more HEK-KWGF cells. When
attached to HEK-KWGF, no spontaneous beating of NCMs was observed,
nor could action potentials be recorded from those NCMs. Upon triggering by
a depolarizing current, however, action potentials could be elicited that
displayed an aberrant morphology when compared to monocultures of NCMs
(Fig. 2a). Application of the gap-junction blocker Halothane to NCM/HEK-
KWGF cell pairs decreased RMP of the NCM to its normal value and restored
spontaneous action potential formation and beating behavior (Fig. 2b).
Fig. 2.
Electrotonic coupling between HEK-KWGF and neonatal cardiomyocyte
(NCM).
a
Action potential recordings from spontaneous NCM mono-cultures (
left
panel
) and triggered NCM/HEK-KWGF cell pair (
right panel
) as measured from the
NCM. Note the diffrrence in resting membrane potential (RMP), action potential
upstroke and duration.
b
Gap-junction uncoupling by halothane restores RMP and
spontaneous action potentials in NCM/HEK-KWGF cell pair as measured from the
NCM. Scale bars—horizontal = 500 ms, vertical = 50 mV,
dashed line
indicates
0 mV.
