Rapid Pacing Decreases L-type Ca2+ Current and Alters Cacna1c Isogene Expression in Primary Cultured Rat Left Ventricular Myocytes

Figures

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  Fig. 1. Primary culture (24–32 h) decreases ICaL density. A representative whole-cell current traces of ICaL recorded from freshly isolated myocytes (blue traces, ‘Control 0d’) and myocytes incubated for 24–32 h without pacing (black traces, ‘Control 1d’). B average current–voltage relations of currents similar to those shown in (A). ICaL was quantified by subtracting the peak current from the current at the end of the voltage pulse (at 600 ms). C activation (circles) and steady-state inactivation (boxes) of ICaL recorded from both groups. D recovery from inactivation of ICaL recorded from both groups. For details regarding pulse protocols see methods section. Note that error bars are smaller than the symbols. 56 ≤ n ≤ 111. *p < 0.05, ***p < 0.001, Control 0d vs. Control 1d

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  Fig. 2. Pacing at 1 or 3 Hz decreases ICaL density. A representative whole-cell current traces of ICaL recorded from myocytes incubated for 24–32 h without pacing (black traces, ‘0 Hz’) and with pacing at 1 Hz (red traces, ‘1 Hz’) and at 3 Hz (green traces, ‘3 Hz’). B average current–voltage relations of currents similar to those shown in (A). ICaL was quantified by subtracting the peak current from the current at the end of the voltage pulse (at 600 ms). Note that most error bars are smaller than the symbols. 48 ≤ n ≤ 76. **p < 0.05, ***p < 0.001, 1 Hz vs. 0 Hz. ###p < 0.001, 3 Hz vs. 0 Hz

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  Fig. 3. Pacing at 1 or 3 Hz alters ICaL kinetics. A activation (circles) and steady-state inactivation (boxes) of ICaL recorded from myocytes incubated for 24–32 h without pacing (black, ‘0 Hz’) and with pacing at 1 Hz (red, ‘1 Hz’) and at 3 Hz (green, ‘3 Hz’). B recovery from inactivation of ICaL recorded from the groups mentioned above. For details regarding pulse protocols see methods section. Note that most error bars are smaller than the symbols. 50 ≤ n ≤ 71

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  Fig. 4. Effects of pacing on mRNA expression of total cacna1c (exon 5) and exon 1 splice variants. A mRNA expression of exon 5 of freshly isolated myocytes (blue, 0 Hz, 0d) and of myocytes incubated for 24 h without pacing (black, 0 Hz, 1d) and with pacing at 1 Hz (red, 1 Hz, 1d) and at 3 Hz (green, 3 Hz, 1d). 10 ≤ n ≤ 16. B mRNA expression of exon 1a in the same groups as in (A). 3 ≤ n ≤ 16. C mRNA expression of exon 1b in the same groups as in (A). 10 ≤ n ≤ 16. D mRNA expression of exon 1c in the same groups as in (A). 10 ≤ n ≤ 16. mRNA expression was normalized to the level of freshly isolated myocytes (blue, 0 Hz, 0d) in each individual experiment. *p < 0.05, **p < 0.05, ***p < 0.001