Extended Data Fig. 3: Treatment of myocytes with propionate in vitro remodels the coupling of action potentials and Ca2+ transients in the absence of hypertrophy.
(a) Sulforhodamine B (SRB) staining of NRVMs treated with propionate (PRO), its 3-hydroxylated derivative (3-OH-PRO) or phenylephrine (PE; pro-hypertrophic agonist) for 48-h. (A) Exemplar images of DAPI and SRB co-staining in control (CON), PRO (4.7 mM) and PE. (b) Ratiometric SRB growth index (eSRB, extra-nuclear SRB signal; nSRB, nuclear SRB signal). N = 6 biologically independent measurements from 6 isolations, with each measurement determined from technical quadruplicates. Ordinary one-way ANOVA with Dunnett’s multiple comparisons test. **** P < 0.0001. Mean ± SEM. (c) Fluorescence imaging of wild-type rat myocytes treated with exogenous propionate. Averaged time-courses of electrically-evoked action potentials (AP; dotted line) and Ca2+ transients (CaT; solid line) made in FluoVolt or Fluo3-loaded neonatal rat (nr) ventricular myocytes respectively, treated for 48-h under control (CON) or 6 mM propionate (PRO) conditions under steady-state pacing at 2 Hz. Time-courses shown as mean only (N = 47–58 myocytes from 7 isolations for FluoVolt, and N = 104–109 myocytes from 9 isolations for Fluo-3). (d) Action potential duration at 90% repolarisation (APD90) and time to 90% CaT recovery (CaT90). Hierarchical analysis of N = 47–58 myocytes from 7 isolations for FluoVolt, and N = 104-109 myocytes from 9 isolations for Fluo-3 shown as mean ± SEM. Two-sided, two sample T-test corrected for hierarchical analysis. **** P < 0.0001.
