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Reduced mechanical efficiency in left-ventricular trabeculae of the spontaneously hypertensive rat.

Han JC, Tran K, Johnston CM, Nielsen PM, Barrett CJ, Taberner AJ, Loiselle DS - Physiol Rep (2014)

Bottom Line: Our results show that, whereas the performance of the SHR-F differed little from that of the SHR-NF, both SHR groups performed less stress-length work than that of Wistar trabeculae.Their lower work output arose from reduced ability to produce sufficient force and shortening.Consequently, mechanical efficiency (the ratio of work to change of enthalpy) of both SHR groups was lower than that of the Wistar trabeculae.

View Article: PubMed Central - PubMed

Affiliation: Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand.

No MeSH data available.


Related in: MedlinePlus

Kinetics of isometric contractions at steady states. (A) Twitch durations at 5% (t5) and at 50% (t50) of peak stress as functions of active stress. (B) Maximal rate of rise (+dS/dt) and rate of fall (−dS/dt) of active stress, computed, respectively, from the ascending and descending limbs of the twitch, were plotted as functions of active stress. (C) Stress‐time integral (STI; the area under the twitch) as a function of active stress. *P < 0.05 for Wistar versus both spontaneously hypertensive rat (SHR) groups, +P < 0.05 for failing SHR (SHR‐F) versus nonfailing SHR (SHR‐NF). Data (mean ± SE) at Lo were superimposed on appropriate panels to demonstrate variability of each average regression line. The insets show data from a representative SHR‐NF trabecula.
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fig02: Kinetics of isometric contractions at steady states. (A) Twitch durations at 5% (t5) and at 50% (t50) of peak stress as functions of active stress. (B) Maximal rate of rise (+dS/dt) and rate of fall (−dS/dt) of active stress, computed, respectively, from the ascending and descending limbs of the twitch, were plotted as functions of active stress. (C) Stress‐time integral (STI; the area under the twitch) as a function of active stress. *P < 0.05 for Wistar versus both spontaneously hypertensive rat (SHR) groups, +P < 0.05 for failing SHR (SHR‐F) versus nonfailing SHR (SHR‐NF). Data (mean ± SE) at Lo were superimposed on appropriate panels to demonstrate variability of each average regression line. The insets show data from a representative SHR‐NF trabecula.

Mentions: Both groups of SHR trabeculae produced lower stresses than that of Wistar trabeculae, as evidenced by their lower average total and average active stress‐length relations (Fig. 1). The average passive stress‐length relation of the SHR‐F was steeper than the SHR‐NF groups (Fig. 1B). The average heat‐length relations of both SHR groups were also lower than the Wistar group (Fig. 1E). Compared with the Wistar group, both SHR groups also demonstrated prolonged twitch duration (quantified at 5% and at 50% of peak stress), had lower maximal rates of rise and fall of twitch stress, and had smaller values of stress‐time integral (STI, the area under the twitch), as indicated by the respective relations shown in Figure 2. Given these mechanical differences, the heat production (plotted as functions of active stress and STI) of the SHR trabeculae was, surprisingly, not different from that of the Wistar trabeculae (Fig. 3). The average activation heat (predicted by the y‐intercept of the heat‐stress relation; Fig. 3A) was not different among the rat groups. The average values of activation heat were 2.35 kJ·m−3± 0.27 kJ·m−3, 2.30 kJ·m−3 ± 0.30 kJ·m−3, and 2.61 kJ·m−3 ± 0.43 kJ·m−3, respectively for the Wistar, SHR and SHR‐F groups. These values were not different from those predicted from the heat‐STI relation (Fig. 3B; respectively 2.49 kJ·m−3 ± 0.27 kJ·m−3, 2.31 kJ·m−3 ±0.31 kJ·m−3, and 2.54 kJ·m−3 ± 0.44 kJ·m−3).


Reduced mechanical efficiency in left-ventricular trabeculae of the spontaneously hypertensive rat.

Han JC, Tran K, Johnston CM, Nielsen PM, Barrett CJ, Taberner AJ, Loiselle DS - Physiol Rep (2014)

Kinetics of isometric contractions at steady states. (A) Twitch durations at 5% (t5) and at 50% (t50) of peak stress as functions of active stress. (B) Maximal rate of rise (+dS/dt) and rate of fall (−dS/dt) of active stress, computed, respectively, from the ascending and descending limbs of the twitch, were plotted as functions of active stress. (C) Stress‐time integral (STI; the area under the twitch) as a function of active stress. *P < 0.05 for Wistar versus both spontaneously hypertensive rat (SHR) groups, +P < 0.05 for failing SHR (SHR‐F) versus nonfailing SHR (SHR‐NF). Data (mean ± SE) at Lo were superimposed on appropriate panels to demonstrate variability of each average regression line. The insets show data from a representative SHR‐NF trabecula.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4255817&req=5

fig02: Kinetics of isometric contractions at steady states. (A) Twitch durations at 5% (t5) and at 50% (t50) of peak stress as functions of active stress. (B) Maximal rate of rise (+dS/dt) and rate of fall (−dS/dt) of active stress, computed, respectively, from the ascending and descending limbs of the twitch, were plotted as functions of active stress. (C) Stress‐time integral (STI; the area under the twitch) as a function of active stress. *P < 0.05 for Wistar versus both spontaneously hypertensive rat (SHR) groups, +P < 0.05 for failing SHR (SHR‐F) versus nonfailing SHR (SHR‐NF). Data (mean ± SE) at Lo were superimposed on appropriate panels to demonstrate variability of each average regression line. The insets show data from a representative SHR‐NF trabecula.
Mentions: Both groups of SHR trabeculae produced lower stresses than that of Wistar trabeculae, as evidenced by their lower average total and average active stress‐length relations (Fig. 1). The average passive stress‐length relation of the SHR‐F was steeper than the SHR‐NF groups (Fig. 1B). The average heat‐length relations of both SHR groups were also lower than the Wistar group (Fig. 1E). Compared with the Wistar group, both SHR groups also demonstrated prolonged twitch duration (quantified at 5% and at 50% of peak stress), had lower maximal rates of rise and fall of twitch stress, and had smaller values of stress‐time integral (STI, the area under the twitch), as indicated by the respective relations shown in Figure 2. Given these mechanical differences, the heat production (plotted as functions of active stress and STI) of the SHR trabeculae was, surprisingly, not different from that of the Wistar trabeculae (Fig. 3). The average activation heat (predicted by the y‐intercept of the heat‐stress relation; Fig. 3A) was not different among the rat groups. The average values of activation heat were 2.35 kJ·m−3± 0.27 kJ·m−3, 2.30 kJ·m−3 ± 0.30 kJ·m−3, and 2.61 kJ·m−3 ± 0.43 kJ·m−3, respectively for the Wistar, SHR and SHR‐F groups. These values were not different from those predicted from the heat‐STI relation (Fig. 3B; respectively 2.49 kJ·m−3 ± 0.27 kJ·m−3, 2.31 kJ·m−3 ±0.31 kJ·m−3, and 2.54 kJ·m−3 ± 0.44 kJ·m−3).

Bottom Line: Our results show that, whereas the performance of the SHR-F differed little from that of the SHR-NF, both SHR groups performed less stress-length work than that of Wistar trabeculae.Their lower work output arose from reduced ability to produce sufficient force and shortening.Consequently, mechanical efficiency (the ratio of work to change of enthalpy) of both SHR groups was lower than that of the Wistar trabeculae.

View Article: PubMed Central - PubMed

Affiliation: Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand.

No MeSH data available.


Related in: MedlinePlus