The Contractile Function of Ventricular Cardiomyocytes Is More Sensitive to Acute 17β-Estradiol Treatment Compared to Atrial Cardiomyocytes

Figures

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  Figure 1. Effects of 17β-estradiol (E2) on sarcomere length (SL) dynamics in mechanically non-loaded contracting atrial and ventricular CM. (A) Representative traces of steady-state SL changes in atrial and ventricular CM from the control group (C) and after 15 min incubation with E2; (B) End-diastolic SL (EDSL); (C) Fractional sarcomere shortening (FS); (D) Maximum velocity of sarcomere shortening (SL vshort); (E) Maximum velocity of sarcomere relengthening (SL vrel); (F) Time-to-peak sarcomere shortening (SL TTP); (G) Time to 50% sarcomere relengthening (SL TTR50). A—atrial CM; V—ventricular CM. Data are presented as violin plots: bold line shows median, dashed lines indicate an Q1–Q3 interval. n/N (number of CM from N hearts) is shown on the B panel. Each dot represents individual CM. The Mann–Whitney U-test is used to compare C and E2 groups.

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  Figure 2. Effects of 17β-estradiol (E2) on cytosolic [Ca2+]i transients in single mechanically non-loaded atrial and ventricular CM. (A) Representative traces of steady-state [Ca2+]i transients in CM from the control group (C) and after 15 min incubation with E2; (B) An amplitude of [Ca2+]i transients ([Ca2+]i Ampl); (C) Time-to-peak [Ca2+]i transients ([Ca2+]i TTP); (D) Time to 50% [Ca2+]i decay ([Ca2+]i TTD50). A—atrial CM; V—ventricular CM. Data are presented as violin plots: bold line shows median, dashed lines indicate an Q1–Q3 interval. n/N (number of CM from N hearts) is shown on the B panel. Each dot represents an individual CM. The Mann–Whitney U-test is used to compare C and E2 groups.

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  Figure 3. Effects of 17β-estradiol (E2) on the tension-length dependence in single ventricular CM. (A) Scheme of CM fixation by four carbon fibers (CF); (B) Representative photo of single ventricular CM attached to carbon fibers (top view); (C) Representative tension–length relationships in single CM from the control group (C) and after 15 min incubation with E2. To obtain the slopes of end-diastolic (passive) tension–length relationship (EDTLR), end-systolic (total) tension–length relationship (ESTLR), and active tension–length relationship (ATLR), the tension magnitudes were fitted by linear regression against the end-diastolic effective cell length for EDTLR and end-systolic effective cell length for ESTLR and ATLR (cell length was expressed in % by initial cell length before the stretch); (D) Tension amplitudes at the initial cell length before the stretch; (E) The slopes of ATLR. (F) The slopes of EDTLR; (G) The slopes of ESTLR. (H) Frank–Starling gain index (FSG) Frank–Starling gain (FSG) index calculated as ESTLR/EDTLR. Data are presented as violin plots: bold line shows median, dashed lines indicate an Q1–Q3 interval. n/N (number of CM from N hearts) is shown on the C panel. Each…

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  Figure 4. Effects of 17β-estradiol (E2) on sarcomeric contractile proteins, extracted from atrial and ventricular CM. (A) Sliding velocity of F-actin over myosin in the in vitro motility assay; (B) Representative gel stained with Pro-Q Diamond and SYPRO Ruby from the control group (C) and after 15 min incubation with E2: M—marker of molecular weight, cMyBP-C—cardiac myosin-binding protein C, TnT—troponin T, Tpm—tropomyosin, TnI—troponin I, aELC and vELC—atrial and ventricular essential light chain of myosin; aRLC and vRLC—atrial and ventricular myosin regulatory light chain; (C) cMyBP-C phosphorylation; (D) ELC phosphorylation; (E) RLC phosphorylation; (F) TnI phosphorylation; (G) Tpm phosphorylation; (H) TnT phosphorylation. A—atrial CM; V—ventricular CM. Data are presented as violin plots: bold line shows median, dashed lines indicate an Q1–Q3 interval. n/N—number of measurements from N hearts. The Mann–Whitney U-test is used to compare C and E2 groups.