Figure 4.
Increased NCX function in patients with cAF. (A) Representative examples of caffeine-evoked Ca2+ transients (CaT) in voltage-clamped (at –80 mV) atrial myocytes from patients in sinus rhythm (SR) or cAF. (B) Bar graphs showing no significant differences in sarcoplasmic reticulum Ca2+ content evidenced by caffeine-evoked CaT amplitude and integrated Na2+/Ca2+-exchange current (INCX). The non-significantly smaller caffeine-evoked CaT amplitude, but unaltered integrated INCX current in cAF points to a potentially higher Ca2+-buffering capacity in cAF vs. SR patients, but this requires further validation in subsequent work (see text for further details). (C) Western blots showing increased NCX1 expression levels in cAF. (D) INCX evoked by caffeine application reveals a greater INCX for a given [Ca2+]i in AF vs. SR patients. (E) Bar graphs showing an increased slope of the INCX and faster decay of caffeine-evoked CaT in cAF as indices of increased functional NCX. (F) Trend toward increased INCX peak current in cAF. Numbers within parentheses indicate myocytes/patients. Reproduced with permission from Voigt et al.43