Synapse
⌘+K
Synapse
PulseExploreClubsResearchersJournals
Instagram
HomeClubsExplore
September 30, 2002The Journal of PhysiologyOpen Access

Myofilament‐based relaxant effect of isoprenaline revealed during work‐loop contractions in rat cardiac trabeculae

View Full Paper
Ask AI
Bookmark
Share

Key result

Isoprenaline reduced diastolic stress from 58.6 to 28.8 mN mm(-2) at 1.5 Hz during work-loop contractions in rat cardiac trabeculae, increasing the frequency for maximum power output.

Population

Isolated rat cardiac trabeculae

Comparison

Isoprenaline during work-loop contractions with… vs Isometric contractions under the same conditions

Design

Preclinical

Authors

JLJoanne LaylandRoyal Adelaide HospitalJKJonathan C. KentishKing's College London

Discussion

Loading...

Member takes

Implication

Beta-adrenergic lusitropy during dynamic loading merits in vivo validation; leaves open translation to human cardiac performance.

Key Points

  • To investigate the contribution of myofilament properties to beta-adrenergic relaxation in isolated cardiac muscle during work-loop contractions compared to isometric conditions.
  • Evaluated isolated rat cardiac trabeculae undergoing isometric or work-loop contractions across stimulation frequencies between 0.25 and 4.5 Hz.
  • Inhibited sarcoplasmic reticulum calcium cycling by pretreating preparations with 1 µM ryanodine and 30 µM cyclopiazonic acid prior to isoprenaline exposure.
  • During sarcoplasmic reticulum inhibition, isoprenaline increased force without altering twitch kinetics in isometric contractions.
  • In work-loop contractions, isoprenaline reduced diastolic stress between beats (decreasing from 58.6 ± 5.5 to 28.8 ± 5.8 mN mm⁻² at 1.5 Hz), reducing the work required for muscle re-lengthening.
  • The relaxant effect increased net work and power output at higher frequencies, shifting the frequency for maximum power output from 1.1 ± 0.1 to 1.6 ± 0.1 Hz.

Structured PICO

P
Population
Isolated rat cardiac trabeculae
I
Intervention
Isoprenaline (beta-adrenergic stimulation) during work-loop contractions with sarcoplasmic reticulum inhibition (ryanodine 1 microM and cyclopiazonic acid 30 microM)
C
Comparator
Isometric contractions under the same conditions
O
Outcome
Contractile force, relaxation time course, diastolic force, net work, and power output at different stimulation frequencies (0.25-4.5 Hz)surrogate

Main Result

Absolute Event Rate: 28.8% vs 58.6%

The relaxant effect of beta-adrenergic stimulation involves myofilament properties that are particularly significant during simultaneous force and length changes, as occurs in the intact heart.

Cite This Study

Layland et al. (2002) studied this question. Isoprenaline (during SR inhibition with ryanodine and cyclopiazonic acid) vs. Baseline was evaluated on Diastolic stress at 1.5 Hz during work-loop contractions. Isoprenaline reduced diastolic stress from 58.6 to 28.8 mN mm(-2) at 1.5 Hz during work-loop contractions in rat cardiac trabeculae, increasing the frequency for maximum power output.

synapsesocial.com/papers/6a1596ac79ff98d0de4eda1ehttps://doi.org/10.1113/jphysiol.2002.022855
View Full Paper
Ask AI
Bookmark
Share

Also Consider

Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context:

  1. 1Intracellular mechanisms mediating reversal of beta-adrenergic stimulation in intact beating hearts1993 · 54 citations
  2. 2Relaxation and diastole of the heart1989 · 338 citations
  3. 3Phosphorylation of Troponin I Controls Cardiac Twitch Dynamics2002 · 123 citations
  4. 4Expression of Slow Skeletal Troponin I in Hearts of Phospholamban Knockout Mice Alters the Relaxant Effect of β-Adrenergic Stimulation2002 · 54 citations
  5. 5Beta-adrenergic receptor stimulation increases unloaded shortening velocity of skinned single ventricular myocytes from rats.1994 · 199 citations