**3.5 Non quantitative ion channel expression profile**

80 Toxicity and Drug Testing

NRHT

\*

NRHT

NRHT

0

50

100

**Titin expression (% of FBME d0)**

150

200

250

EHT d0

EHT d3

EHT d6

\* \*

EHT d9

EHT d12

EHT d15

ARH

\*

0

100

**Ncx expression (% of FBME d0)**

200

EHT d0

EHT d3

\* \*

EHT d6

EHT d9

EHT d12

EHT d15

ARH

\*

**Beta-MHC expression (% of FBME d0)**

EHT d0

\* \*

\*

EHT d3

EHT d6

\*

EHT d9

EHT d12

\* \*

EHT d15

ARH

NRHT

NRHT

NRHT

\*

0

100

**Alpha-MHC expression (% of FBME d0)**

200

EHT d0

EHT d3

EHT d6

EHT d9

EHT d12

EHT d15

ARH

\*

**Serca expression (% of FBME d0))**

EHT d0

\* \*

EHT d3

EHT d6

EHT d9

EHT d12

\*

EHT d15

ARH

\*

0

50

100

**Alpha actinin expression (% of FBME d0)**

150

EHT d0

EHT d3

EHT d6

EHT d9

\*

\*

EHT d12

\*

EHT d15

ARH

Fig. 6. RT-qPCR of FBMEs in comparison to neonatal (NRHT) and adult rat heart (ART). ∆∆CT values were generated by normalisation to the mRNA of cardiac specific protein calsequestrin 2 (average CT values for normalisation were as follows: d0: 20.8, d3: 20.4, d6: 20.6, d9: 21.3, d12: 21.6, d15: 20.5). Figures show relative expression compared to day 0. Each bar represents results from 4 biological replicates (each measured 3 times). \* p<0.05 vs.

day 15 (Student's t test). Bars show means +/- SEM (Hansen et al. 2010).

Ion channels play an important role as targets of proarrhythmic drugs. To determine whether the principal ion channel subunits known from human hearts are expressed in rat FBMEs transcripts of 23 ion channel α-subunits (7 calcium channels, 6 sodium channels, 10 potassium channels) were amplified from total RNA of FBMEs and a nonfailing human heart sample by RT-PCR (35 cycles). 22/23 transcripts were amplified from both sources, one channel (CacnA1I) was neither amplified in FBMEs nor in the nonfailing human heart (Figure 7).

Fig. 7. Agarose gel of the PCR-products of 23 ion channel subunits. The ion channel profile of FBMEs was compared to the expression profile of a nonfailing human heart. Potassium channels (A), calcium channel (B) and sodium channels (C) showed qualitatively similar results (descriptions indicate the related gene for each channel subunit; for further information see table 1; Hansen et al. 2010).
