Overexpression of miR-1 and miR-133 increases the frequency of pro-arrhythmic spontaneous Ca²⁺ waves (SCW) in rat myocytes.

<p>A, Time dependent profiles of electrically- (field stimulation at 0.5 Hz) and 10 mM caffeine-evoked Ca²⁺ transients in myocytes infected with scrambled and miR-133 carrying Advs (MOI 100) after 48 hrs in primary culture. B,C,D. Pooled data for electrically and caffeine evoked Ca²⁺ transient amplitude and fractional release in miR-133 overexpressing myocytes vs. controls. E. Representative confocal Ca²⁺ images with corresponding time dependent profiles recorded in field-stimulated (0.2 Hz) myocytes in the presence of 100 nM isoproterenol infected with miR-1 and/or miR-133 Adv. F. Pooled data for the number of SCWs per second. *Statistically significant at p<0.05 vs. scrambled, n = 15–25. G. Representative Western Blots (upper panel) and pooled data (lower panel) of PP2AC in myocytes infected with control Adv (scrambled) or miR-1, or miR-133 or both miR-1 and miR-133; *<0.05 vs control, n = 6. H. Levels of miR-1 and miR-133 in myocytes assessed by qRT-PCR. *<0.05 vs control, n = 3. I. Infection of non-muscle cells (HEK) with miR-1 does not result in increase in expression levels of miR-133 and vise versa, *p<0.05 vs control, n = 3.