Figure 5.

Effects of sodium–calcium exchanger (NCX) inhibition with ORM‐10103 on Ca transients and sarcoplasmic reticulum (SR) Ca in the left (LA) and right atria (RA). (A) Typical example of a caffeine‐induced Ca transient after 1 Hz stimulation at baseline (top) and after wash‐in of 3 μM ORM‐10103 (bottom). (B) Rate of Ca removal during caffeine response, k_caff (1/s, single exponential fitting), was slower with ORM‐10103 in all groups (LA: N _CTRL = 2, n = 7; N _DOCA = 2, n = 8; RA: N _CTRL = 2, n = 6; N _DOCA = 3, n = 10). (C) Percentage of forward mode NCX block, calculated from the relative changes in values of caffeine decay constant in (B). (D–F) Detailed analysis of systolic and caffeine‐induced Ca transients at baseline and after application of ORM‐10103; comparison between 11‐deoxycorticosterone acetate (DOCA) LA and RA cardiomyocytes from the same dataset as in Figure 4 . (D) Systolic Ca transient amplitude at 1 Hz. (E) SR [Ca²⁺]_i. (F) Time constant of systolic Ca transient decline, τ in ms, obtained from mono‐exponential fitting. *P < 0.05 vs. baseline; ^# P < 0.05 for comparison between LA and RA. CTRL, control