Panel A shows confocal line-scan recordings of intracellular calcium levels with high-gain myocytes on the left and low-gain myocytes on the right. Panel B shows confocal line-scan recordings of cyto-iATP levels with high-gain myocytes on the left and low-gain myocytes on the right. The dashed line in both panels indicates baseline fluorescence (F/F0= 1). Panel C is a scatter plot showing the time to calcium peak for high-gain and low-gain myocytes. Panel D is a scatter plot showing the calcium decay t 1/2 for high-gain and low-gain myocytes. Panel E is a scatter plot showing the calcium transient duration for high-gain and low-gain myocytes. Panel F is a scatter plot showing the time to cyto-iATP peak for high-gain and low-gain myocytes. Panel G is a scatter plot showing the cyto-iATP decay t 1/2 for high-gain and low-gain myocytes. Panel H is a scatter plot showing the cyto-iATP transient duration for high-gain and low-gain myocytes. Each scatter plot includes large circles denoting per-animal means and small circles indicating individual biological replicates.
High-gain SA node myocytes exhibit prolonged intracellular Ca 2+ transients compared with low-gain myocytes. (A and B) Representative normalized confocal line-scan recordings of intracellular Ca2+ (red, A) and cyto-iATP (green, B) from myocytes classified as high-gain (left) or low-gain (right). The dashed line indicates baseline fluorescence (F/F0 = 1). (C–E) Summary quantification of Ca2+ transient kinetics (high-gain, N = 4; low-gain, N = 5), including time to peak (C), decay t1/2 (D), and transient duration (E). (F–H) Summary quantification of cyto-iATP transient kinetics, including time to peak (F), decay constant (G), and transient duration (H). P values are shown above comparisons. Large circles denote per-animal means; small circles indicate individual biological replicates. N represents the number of independent mice.