Application Note

Channel:Cells:
Tools:hERG
CHO
Port-a-Patch®
External Perfusion

Characterization of hERG (CHO cells) onNanion‘s Port-a-Patch®
The electrophysiology team at Nanion Technologies GmbH, Munich.
Cells were supplied by Millipore, USA

SummaryResults

The hERG gene (KCNH2) encodes a potassium ion chan-Figure 1 shows current responses of an individual cell to anel responsible for the repolarizing IKr current in the car-typical hERG voltage protocol. Potentials were stepped

diac action potential (Sanguinetti et al., 1995).

from the holding potential (-80 mV) for 500 ms to +40 mV
followed by a 500 ms step to voltages ranging from

Abnormalities in this channel may lead to either Long QT-120 mV to +40 mV (20 mV steps), before stepping backSyndrome (LQT2) (with loss-of-function mutations) or Shortto holding.

QT syndrome (with gain-of-function mutations), both po-Figure 2 shows the corresponding normalized current-volt-

tentially fatal cardiac arrhythmia, due to repolarization

age relation. The averaged mean current of the cells was

disturbances of the cardiac action potential.

510.59 ± 73 pA at 40mV (n=41).

Given the importance of this channel in maintaining cardiac function, it has become an important target in compound safety screening.
A large range of therapeutic agents with diverse chemical structures have been reported to induce long QT syndrome. These include antihistamines (e.g. Terfenadine),gastrointestinal prokinetic agents (e.g. Cisapride) andothers.
In this report we present data that were collected on thePort-a-Patch®. Cells (CHO permanently expressing hERG,
supplied by Millipore) were tested. Current amplitudes, IVs
and cisapride as well as quinidine dose response curves
were analyzed.

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Figure 1:
Representative current responses of an individual cell to a hERG IV voltage protocol (for details see text above).

Application Note

Figure 4:
Raw current traces in the presence of increaseing concentraitons ofquinidine.
Figure 2:
Average normalized current- voltage relationship (n=10, holding potential -80 mV. The error bars depict the standard error of the mean).

Figure 5:
Full quinidine and cisapride dose response curves.
Figure 3:
Development of the peak current at -40 mV over time after thawing ofthe cells. Each day between three and five cells were measured.

With Nanion‘s External Perfusion System also cumulative

Since cell lines permanently expressing hERG sometimes

does-response curves were collected for quinidine andhave rather small currents it was tested whether the cultur-cisapride. Raw current responses in the presence of dif-

ing time after thawing had an effect on the current ampli-ferent quinidine concentrations are shown in Figure 4. Av-tudes. As visible in Figure 3, the maximum current ampli-

erage dose-response curves for quinidine and cisapride

tude was rather variably, both within a day and over theare shown in Figure 5. From these, IC50s of 267 ± 68 nM andwhole period. Remarkably is the continuous increase of

31.5 ± 6.2 nM were determined for quinidine and cisap-

the peak current over the experimental time frame.

ride, respectively.

Methods

Electrophysiology

Cells

Whole cell patch clamp recordings were conducted ac-CHO stably expressing hERG were supplied by Millipore.
Cell culture

cording to Nanion’s standard procedure for the Port-aPatch®. Currents were elicited using a voltage step froma holding potential of -80 mV to +40 mV for 500 ms fol-Cells were cultured and harvested according to Nan-lowed by a step to the test potential for 500 ms and backion‘s standard cell culture protocol.

to holding. Voltage protocols were elicited every 20 s.

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