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Tension cost correlates with mechanical and biochemical parameters in different myocardial contractility conditions.

Moreira CM, Meira EF, Vestena L, Stefanon I, Vassallo DV, Padilha AS - Clinics (Sao Paulo) (2012)

Bottom Line: The results obtained from infarcted, diabetic, and deoxycorticosterone acetate-salt-treated rats showed reductions in twitch and tetanic tension compared to the control and sham-operated groups.In the studied conditions (e.g., post-myocardial infarction, deoxycorticosterone acetate salt-induced hypertension, chronic N-nitro-L-arginine methyl ester treatment, and streptozotocin-induced diabetes), a positive correlation between force or plateau tetanic tension and myosin ATPase activity was observed.Our results suggest that the myocardium adapts to force generation by increasing or reducing the tension cost to maintain myocardial contractility with a better mechanical advantage.

View Article: PubMed Central - PubMed

Affiliation: Universidade Federal do Pampa, Uruguaiana, RS, Brasil.

ABSTRACT

Objectives: Tension cost, the ratio of myosin ATPase activity to tension, reflects the economy of tension development in the myocardium. To evaluate the mechanical advantage represented by the tension cost, we studied papillary muscle contractility and the activity of myosin ATPase in the left ventricles in normal and pathophysiological conditions.

Methods: Experimental protocols were performed using rat left ventricles from: (1) streptozotocin-induced diabetic and control Wistar rats; (2) N-nitro-L-arginine methyl ester (L-NAME) hypertensive and untreated Wistar rats; (3) deoxycorticosterone acetate (DOCA) salt-treated, nephrectomized and salt- and DOCA-treated rats; (4) spontaneous hypertensive rats (SHR) and Wistar Kyoto (WKY) rats; (5) rats with myocardial infarction and shamoperated rats. The isometric force, tetanic tension, and the activity of myosin ATPase were measured.

Results: The results obtained from infarcted, diabetic, and deoxycorticosterone acetate-salt-treated rats showed reductions in twitch and tetanic tension compared to the control and sham-operated groups. Twitch and tetanic tension increased in the N-nitro-L-arginine methyl ester-treated rats compared with the Wistar rats. Myosin ATPase activity was depressed in the infarcted, diabetic, and deoxycorticosterone acetate salt-treated rats compared with control and sham-operated rats and was increased in N-nitro-L-arginine methyl ester-treated rats. These parameters did not differ between SHR and WKY rats. In the studied conditions (e.g., post-myocardial infarction, deoxycorticosterone acetate salt-induced hypertension, chronic N-nitro-L-arginine methyl ester treatment, and streptozotocin-induced diabetes), a positive correlation between force or plateau tetanic tension and myosin ATPase activity was observed.

Conclusion: Our results suggest that the myocardium adapts to force generation by increasing or reducing the tension cost to maintain myocardial contractility with a better mechanical advantage.

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Related in: MedlinePlus

Effects of myocardial infarction (A), hypertension (B), diabetes (C), DOCA-salt-induced hypertension (D), and chronic L-NAME treatment (E) on myosin ATPase activity (nmol/Pi/min/mg) in the rat left ventricle. The results represent the means ± SEM, and N indicates the number of experiments. *p<0.05 vs. control (t-test or one-way ANOVA, repeated measurements).
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f3-cln_67p489: Effects of myocardial infarction (A), hypertension (B), diabetes (C), DOCA-salt-induced hypertension (D), and chronic L-NAME treatment (E) on myosin ATPase activity (nmol/Pi/min/mg) in the rat left ventricle. The results represent the means ± SEM, and N indicates the number of experiments. *p<0.05 vs. control (t-test or one-way ANOVA, repeated measurements).

Mentions: Four weeks after myocardial infarction, the isometric force development (Figure 1A) and peak and plateau tetanic tension (Figure 2A), Table 3 were reduced. The level of myosin ATPase activity was also reduced compared to that observed in sham-operated rats (Figure 3A).


Tension cost correlates with mechanical and biochemical parameters in different myocardial contractility conditions.

Moreira CM, Meira EF, Vestena L, Stefanon I, Vassallo DV, Padilha AS - Clinics (Sao Paulo) (2012)

Effects of myocardial infarction (A), hypertension (B), diabetes (C), DOCA-salt-induced hypertension (D), and chronic L-NAME treatment (E) on myosin ATPase activity (nmol/Pi/min/mg) in the rat left ventricle. The results represent the means ± SEM, and N indicates the number of experiments. *p<0.05 vs. control (t-test or one-way ANOVA, repeated measurements).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3351267&req=5

f3-cln_67p489: Effects of myocardial infarction (A), hypertension (B), diabetes (C), DOCA-salt-induced hypertension (D), and chronic L-NAME treatment (E) on myosin ATPase activity (nmol/Pi/min/mg) in the rat left ventricle. The results represent the means ± SEM, and N indicates the number of experiments. *p<0.05 vs. control (t-test or one-way ANOVA, repeated measurements).
Mentions: Four weeks after myocardial infarction, the isometric force development (Figure 1A) and peak and plateau tetanic tension (Figure 2A), Table 3 were reduced. The level of myosin ATPase activity was also reduced compared to that observed in sham-operated rats (Figure 3A).

Bottom Line: The results obtained from infarcted, diabetic, and deoxycorticosterone acetate-salt-treated rats showed reductions in twitch and tetanic tension compared to the control and sham-operated groups.In the studied conditions (e.g., post-myocardial infarction, deoxycorticosterone acetate salt-induced hypertension, chronic N-nitro-L-arginine methyl ester treatment, and streptozotocin-induced diabetes), a positive correlation between force or plateau tetanic tension and myosin ATPase activity was observed.Our results suggest that the myocardium adapts to force generation by increasing or reducing the tension cost to maintain myocardial contractility with a better mechanical advantage.

View Article: PubMed Central - PubMed

Affiliation: Universidade Federal do Pampa, Uruguaiana, RS, Brasil.

ABSTRACT

Objectives: Tension cost, the ratio of myosin ATPase activity to tension, reflects the economy of tension development in the myocardium. To evaluate the mechanical advantage represented by the tension cost, we studied papillary muscle contractility and the activity of myosin ATPase in the left ventricles in normal and pathophysiological conditions.

Methods: Experimental protocols were performed using rat left ventricles from: (1) streptozotocin-induced diabetic and control Wistar rats; (2) N-nitro-L-arginine methyl ester (L-NAME) hypertensive and untreated Wistar rats; (3) deoxycorticosterone acetate (DOCA) salt-treated, nephrectomized and salt- and DOCA-treated rats; (4) spontaneous hypertensive rats (SHR) and Wistar Kyoto (WKY) rats; (5) rats with myocardial infarction and shamoperated rats. The isometric force, tetanic tension, and the activity of myosin ATPase were measured.

Results: The results obtained from infarcted, diabetic, and deoxycorticosterone acetate-salt-treated rats showed reductions in twitch and tetanic tension compared to the control and sham-operated groups. Twitch and tetanic tension increased in the N-nitro-L-arginine methyl ester-treated rats compared with the Wistar rats. Myosin ATPase activity was depressed in the infarcted, diabetic, and deoxycorticosterone acetate salt-treated rats compared with control and sham-operated rats and was increased in N-nitro-L-arginine methyl ester-treated rats. These parameters did not differ between SHR and WKY rats. In the studied conditions (e.g., post-myocardial infarction, deoxycorticosterone acetate salt-induced hypertension, chronic N-nitro-L-arginine methyl ester treatment, and streptozotocin-induced diabetes), a positive correlation between force or plateau tetanic tension and myosin ATPase activity was observed.

Conclusion: Our results suggest that the myocardium adapts to force generation by increasing or reducing the tension cost to maintain myocardial contractility with a better mechanical advantage.

Show MeSH
Related in: MedlinePlus