![Superior SA node myocytes exhibit elevated diastolic ATP and metabolic flux compared with the inferior region. (A) 3D segmented maximum-intensity projection of a whole-mount SA node immunolabeled for CD31 (vasculature, red) and cyto-iATP (myocytes, green). The dashed line denotes the boundary between superior and inferior regions. (B) Image-processing workflow illustrating merged maximum-intensity projections, binary segmentation masks, and extraction of grayscale cyto-iATP signals used for quantitative analysis. (C) Mean cyto-iATP fluorescence intensity per myocyte, grouped by region (N = 5 mice per region), reporting expression levels of the EGFP-tagged cyto-iATP sensor. (D) Live confocal imaging of cyto-iATP signals showing representative line-scan images and corresponding normalized fluorescence traces (F/F0) from superior and inferior regions. (E and F) Summary quantification of cyto-iATP signal mass rate (E) and estimated diastolic [ATP]i (F). 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. Refer to the image caption for details.](https://cdn.rupress.org/rup/content_public/journal/jgp/158/3/10.1085_jgp.202513874/1/jgp_202513874_fig1.png?Expires=1778002717&Signature=Gk-phErR5lowYGm9bHKewWlKqDeRNyFBbVDY6Y7fG4F-LPwlSfyCItCKGGtuC1RiGv23Ih2QUp8TEVx6Rs2wbNpmAE0rkHn7YcHJX9TvrpEXDwZJYY3zeX1BNzd7dmR-0QfVEoTNRGoknKGhjzYtbO~Q1GmnJ94MM3gYyI0KT8PpMqSSgSMOOFKAQbwGsjd2H-v6d5za-0ULvQpzF7NX3Prlg2Ofc~VZKE2pqPwqJULcM69mwj2Ijvt1JwOrN6Oduqf1cXD83f9r6FNn1cEYsmlAIKrgxJgkTaQ~6k4PxjS9XawoBanfXlPEByVjAwhLd3RXS3t5PnbFgBGwNCQYoA__&Key-Pair-Id=APKAIE5G5CRDK6RD3PGA)
Panel A shows a 3D segmented maximum-intensity projection of CD31-labeled vasculature and cyto-iATP–expressing myocytes in a whole-mount SA node, separating superior and inferior regions. Panel B shows merged projections, binary cyto-iATP segmentation, and grayscale signal maps for superior and inferior SA node. Panel C shows scatter plot of mean EGFP fluorescence per cell comparing superior and inferior SA node. Panel D shows live confocal imaging of cyto-iATP imaging with line-scan fluorescence traces indicating oscillatory metabolic activity differences between regions. Panel E shows cyto-iATP signal mass rate comparison between superior and inferior SA node. Panel F shows the estimated diastolic intracellular ATP concentration plotted for superior and inferior SA node.
Superior SA node myocytes exhibit elevated diastolic ATP and metabolic flux compared with the inferior region. (A) 3D segmented maximum-intensity projection of a whole-mount SA node immunolabeled for CD31 (vasculature, red) and cyto-iATP (myocytes, green). The dashed line denotes the boundary between superior and inferior regions. (B) Image-processing workflow illustrating merged maximum-intensity projections, binary segmentation masks, and extraction of grayscale cyto-iATP signals used for quantitative analysis. (C) Mean cyto-iATP fluorescence intensity per myocyte, grouped by region (N = 5 mice per region), reporting expression levels of the EGFP-tagged cyto-iATP sensor. (D) Live confocal imaging of cyto-iATP signals showing representative line-scan images and corresponding normalized fluorescence traces (F/F0) from superior and inferior regions. (E and F) Summary quantification of cyto-iATP signal mass rate (E) and estimated diastolic [ATP]i (F). 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.