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Calcium sensitivity and cardiac performance in genetic and renal models of hypertension
Insights
This study compared cardiac function in spontaneously hypertensive rats (SHR) and renal hypertensive rats (RHR). Results suggest inherited hypertension may involve abnormal cardiac calcium utilization, unlike acquired hypertension.
Area of Science:
- Cardiovascular Physiology
- Hypertension Research
- Cardiac Pharmacology
Background:
- Hypertension leads to cardiac hypertrophy and altered heart function.
- Understanding differences between inherited and acquired hypertension is crucial for targeted therapies.
Purpose of the Study:
- To compare cardiac performance, hypertrophy, and sensitivity to calcium and verapamil in spontaneously hypertensive rats (SHR) and renal hypertensive rats (RHR).
- To investigate potential differences in cardiac calcium utilization between inherited and acquired forms of hypertension.
Main Methods:
- Isolated perfused heart preparation in six-to-nine-month-old SHR, RHR, and age-matched control rats.
- Measurement of cardiac output, heart rate, mean blood pressure, and heart weight.
- Assessment of cardiac response to varying calcium concentrations ([Ca2+]) and verapamil.
Main Results:
- Both SHR and RHR showed increased cardiac output, mean blood pressure, and heart weight compared to controls.
- SHR hearts demonstrated preserved cardiac output at high aortic pressure and altered responses to low and high calcium concentrations.
- Verapamil significantly reduced cardiac responsiveness in RHR and controls but not in SHR.
Conclusions:
- Cardiac performance differs between spontaneously hypertensive rats (inherited) and renal hypertensive rats (acquired).
- Findings suggest an abnormality in cardiac calcium utilization specific to inherited hypertension (SHR).
- Acquired hypertension (RHR) appears to have different mechanisms affecting cardiac calcium sensitivity.
Abstract:
We have compared cardiac performance, hypertrophy and sensitivity to calcium and verapamil of hearts of six to nine-month-old spontaneously hypertensive rats (SHR), two-kidney, one clip renal hypertensive rats (RHR) and age-matched controls. Cardiac output and heart rate were measured using an isolated perfused heart preparation. Mean blood pressure (BP) and heart weight were equally increased in SHR and RHR as was optimal left atrial filling pressure. Cardiac output was increased in both SHR and RHR at any given work load; this improvement was seen especially in SHR and at high aortic pressure (160 cm H2O) was significant in SHR but not RHR. In low [Ca2+], 0.6 mM, cardiac output of RHR and controls fell markedly, but changed little in SHR, whereas in high [Ca2+], 5.1 mM, cardiac performance deteriorated in SHR but was improved in RHR and controls. Verapamil 2 X 10(-7) M reduced Ca2+ responsiveness of RHR and controls threefold but had no effect in SHR. The results suggest there may be an abnormality of cardiac calcium utilization in inherited but not in acquired hypertension.