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Impaired coronary flow and ventricular function in hearts of hypertensive rats
Insights
Hypertension in rats impairs heart function and coronary blood flow early on. This study shows reduced cardiac performance and coronary vascular reserve in hypertensive rats, highlighting potential long-term heart damage.
Area of Science:
- Cardiovascular Physiology
- Renal Hypertension Research
- Cardiac Function Studies
Background:
- Hypertension is a major risk factor for cardiovascular disease.
- The impact of hypertension on cardiac function and coronary circulation requires further elucidation.
- Understanding early changes in hypertensive hearts is crucial for developing preventative strategies.
Purpose of the Study:
- To investigate the effects of experimentally induced hypertension on cardiac function and coronary blood flow in rats.
- To determine the temporal relationship between the development of hypertension and the onset of cardiac dysfunction.
- To assess alterations in myocardial metabolism and vascular reserve under hypertensive conditions.
Main Methods:
- Induction of hypertension in rats via left renal artery clipping.
- Assessment of cardiac function using an isolated working heart apparatus at multiple time points post-surgery.
- Measurement of coronary flow and myocardial oxygen consumption (MVO2) under normoxic and anoxic conditions.
- Analysis of myocardial actomyosin ATPase activity and biochemical markers (lactate/pyruvate ratio).
Main Results:
- Hypertensive rats exhibited depressed cardiac function, including lower stroke volume, peak systolic pressure, and ejection fraction.
- Significantly reduced coronary blood flow and MVO2 were observed in hypertensive hearts.
- Impaired coronary vascular reserve developed within days of hypertension onset, evident during both normoxic and anoxic perfusion.
- Elevated left ventricular end-diastolic pressure (LVEDP) and depressed myocardial actomyosin ATPase activity were noted in hypertensive rats.
Conclusions:
- Experimental hypertension in rats leads to early impairment of cardiac function and coronary vascular reserve.
- These cardiac and vascular deficits develop rapidly following the onset of hypertension.
- The findings suggest that early interventions may be necessary to mitigate hypertension-induced cardiac damage.
Abstract:
Hearts of rats made hypertensive (BP greater than 150 mmHg) by left renal artery clipping and sham operated controls were studied in two series of experiments. In series I, cardiac function was studied in an isolated working heart apparatus at weeks 4, 9 to 10 and 16 to 17 post-surgery. In series II, coronary flow was studied during normoxic and anoxic retrograde perfusions at days 6 to 9 and at weeks 4 and 10 post-surgery. In series I, when compared with controls, hypertensives had lower body weights at weeks 4 and 9 to 10, and higher left ventricular weights at each period. Heart function was depressed for hypertensives when compared with controls as measured by lower stroke volume, peak left ventricular systolic pressure, stroke work, ejection fraction, positive dP/dt, peak aortic flow, and maximal flow acceleration. Relaxation rate as measured by negative dP/dt was also depressed. Hearts from hypertensives had significantly lower coronary flows and MVO2, and increased percent oxygen extraction and effluent lactate/pyruvate ratios. LVEDP was significantly elevated for hypertensives, when LVEDV (ml) was similar for hypertensives and controls. Myocardial actomyosin ATPase activity was depressed for hypertensives at weeks 9 to 10 and 16 to 17 post-surgery. In series II, when hearts were perfused retrogradely, coronary flow was lower for hypertensives than for controls during normoxia at days 6 to 9 and at week 4, and during anoxia at all time periods. The findings demonstrate that impaired coronary vascular reserve develops within days of the development of hypertension in rats, and this can be associated with impaired ventricular function.