Panel A: Image showing FAD autofluorescence distribution in mouse SA node tissue. Superior and inferior regions are outlined, illustrating spatial metabolic organization. Panel B: Scatter plot showing fold-change in FAD autofluorescence in superior SA node. Responses are measured during If inhibition, SERCA inhibition, and mitochondrial uncoupling. Panel C: Scatter plot showing fold-change in FAD autofluorescence in inferior SA node. Values compare metabolic responses under ivabradine, thapsigargin, and FCCP treatments.
Distinct mitochondrial redox regulation in the superior versus inferior SA node. (A) Representative FAD autofluorescence image of a mouse SA node illustrating spatial segregation of the superior (yellow outline) and inferior (white outline) regions. Scale bar, 50 µm. (B and C) Quantification of normalized FAD autofluorescence (F/F0) in the superior (B) and inferior (C) SA node under control conditions and following If inhibition with ivabradine (30 µM), SERCA inhibition with thapsigargin (1 µM), or mitochondrial uncoupling with FCCP (1 µM). The dashed line indicates baseline fluorescence (F/F0 = 1). P values are shown above comparisons. P values indicate comparisons relative to baseline (F/F0 = 1). Data are presented as means ± SEM (N = 4 mice). Large circles denote per-animal means; small circles indicate individual biological replicates. N represents the number of independent mice.