Hypertrophied myocardium is more dependent on extracellular calcium than the normal cardiac muscle
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Updated: Jun 10, 2026
Assessment of Myofilament Ca2+ Sensitivity Underlying Cardiac Excitation-contraction Coupling
Published on: August 1, 2016
Reginaldo de Barros1, Leonardo A M Zornoff, Henrique B Ribeiro
1Botucatu Medical School, UNESP-São Paulo State University, Botucatu, Brazil.
Insights
Renovascular hypertension in rats causes hypertrophied myocardial dysfunction, potentially due to altered intracellular calcium handling. This study analyzed myocardial function and its response to inotropic maneuvers in hypertensive rats.
Area of Science:
- Cardiovascular Physiology
- Renal Hypertension Research
- Myocardial Function Analysis
Background:
- Renovascular hypertension (RHT) induces stable myocardial hypertrophy.
- Understanding functional changes in hypertrophied myocardium is crucial.
Purpose of the Study:
- To analyze myocardial function in rats with 10-week renovascular hypertension.
- To assess the response of hypertrophied myocardium to inotropic stimuli.
Main Methods:
- Isolated left ventricle papillary muscles from RHT and control rats were used.
- Isometric contractions were measured under various conditions: post-rest contraction (PRC), extracellular calcium (ECa2+) concentrations, and isoproterenol (ISOP) stimulation.
Main Results:
- RHT rats showed increased resting tension and contraction time (TPT), with a trend for longer relaxation time (RT50).
- PRC and ISOP elicited similar functional responses in both groups.
- ECa2+ shifts altered TPT differently between RHT and control groups, indicating impaired calcium handling in RHT.
Conclusions:
- Hypertrophied myocardial dysfunction in RHT may stem from alterations in intracellular calcium cycling.
- These findings highlight the role of calcium dysregulation in hypertensive heart disease.
Background:
The aim of this study was to analyze stable hypertrophied myocardial function and its response to inotropic maneuvers in rats submitted to renovascular hypertension for a 10-week period (RHT group, n=10).
Material/Methods:
Myocardial performance was studied in isolated left ventricle papillary muscles in isometric contraction under the following conditions: at postrest contraction of 30 seconds (PRC), at extracellular calcium (ECa2+) chloride concentration of 1.25 and 5.20 mM, and after beta-adrenergic stimulation with 10-6 M isoproterenol (ISOP).
Results:
The results were compared with normotensive Wistar controls rats (C group, n=10). In basal condition, resting tension, and contraction time (TPT) were greater, while relaxation time (RT50) tended to be longer in RHT than C group. PRC and ISOP promoted a similar change in muscle function response intensity (delta) in both groups. ECa2+ shift did not change TPT in the C group and decreased TPT in the RHT animals; delta was different between these groups. RT50 increased in C and decreased in RHT, both without statistical significance; however, delta was different.
Conclusions:
These results suggest that hypertrophied myocardial dysfunction may be attributed to changes in intracellular calcium cycling.
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