Figure 2.
Ex5 cardiomyocytes have attenuated KATP channel activity. A, B) KATP current was measured in WT and Ex5 neonatal cardiomyocytes at baseline (B) and during the application of the KATP channel opener pinacidil (P) and the sulfonylurea blocker glibenclamide (G). A) Raw current traces from Ex5 cardiomyocytes showed little response to either pinacidil or glybenclamide compared to WT cardiomyocytes. B) WT cardiomyocytes displayed a pinacidil-responsive KATP current compared to baseline [0.69±0.19 (n=13) vs. 1.69±0.33 (n=11)]. Ex5 cardiomyocytes lacked this current [0.49±0.15 (n=11) vs. 0.57±0.15 (n=10); P>0.05]. A glibenclamide-sensitive KATP current was only seen in WT cardiomyocytes [0.69±0.19 (n=13) vs. 0.51±0.14 (n=10)]. *P < 0.05, 1-way ANOVA. C) To test mitochondrial KATP channel function, WT and Ex5 neonatal cardiomyocytes were loaded with the mitochondrial voltage-sensitive dye TMRE, and the mitochondrial response to a KATP opener, diazoxide, was measured. TMRE fluorescence declined during diazoxide application to WT cells, suggesting a robust mitochondrial KATP channel response, while Ex5 mitochondria exhibited a significantly attenuated response consistent with reduction of mitochondrial KATP activity.