Panel A contains four line graphs showing total buffering capacity, intrinsic buffering, and Fura-2 buffering. The x-axis represents cytosolic calcium ion concentration in micromolar, and the y-axis represents the calcium ion-binding ratio. Lines indicate fits derived from buffering analysis. Panel B contains two line graphs showing calculated total bound calcium ions as a function of cytosolic calcium ion concentration in left ventricular cardiomyocytes and right ventricular cardiomyocytes. Solid lines indicate control cells, dashed lines indicate SMTC-treated cells, and shaded areas represent differences in bound calcium ions between conditions below 2 micromolar. Panel C contains a bar graph summarizing total endogenous calcium ion buffer concentration in left and right ventricular cardiomyocytes with or without SMTC. The y-axis represents total buffer concentration in micromoles per liter. Panel D contains a bar graph summarizing intracellular Fura-2 concentration across experimental groups. The y-axis represents Fura-2 concentration in micromoles per liter. Panel E contains a bar graph summarizing the apparent dissociation constant of endogenous calcium ion buffers. The y-axis represents the dissociation constant in micromolar. Individual dots represent values from independent experiments.
Effects of SMTC on cytosolic Ca 2+ buffering properties in LVCM and RVCM. (A) Ca2+-binding ratio () plotted as a function of intracellular Ca2+ concentration () in LVCM, LVCM + SMTC, RVCM, and RVCM + SMTC. Total buffering capacity (circles), intrinsic buffering (squares), and fura-2 buffering (triangles) are shown. Lines indicate fits derived from buffering analysis (Eq. 1 and Eq. 2). (B) Calculated total bound Ca2+ as a function of [Ca2+]c in LVCM (top) and RVCM (bottom). Solid lines indicate calculated values for control cells, and dashed lines indicate calculated values for SMTC-treated cells. Shaded areas represent the difference in bound Ca2+ between control and SMTC conditions across the measured Ca2+ range (<2 µM). (C) Summary of total endogenous Ca2+ buffer concentration ([S]tot) in LVCM and RVCM with (S) or without (C) SMTC. No significant differences were detected between groups. (D) Summary of intracellular fura-2 concentration ([fura-2]tot) across experimental groups. SMTC treatment did not affect indicator loading in either LVCM or RVCM. (E) Apparent dissociation constant () of endogenous Ca2+ buffers. SMTC significantly reduced in both LVCM and RVCM, with a more pronounced effect in RVCM. Individual dots represent values from independent experiments. For all groups, N = 6 independent experiments and n = 6 cells per group.