Alterações cardiovasculares de fêmeas de ratos espontaneamente hipertensos (SHR) relacionadas com a idade / Cardiovascular changes in female spontaneously hypertensive rats (SHR) age-related

AUTOR(ES)
DATA DE PUBLICAÇÃO

2011

RESUMO

Hypertension is a major cause of cardiovascular disorders, and the natural progression of this disease may trigger further changes in the circulatory system. Experimental models are widely used in studies on the changes that occur in the cardiovascular system induced by hypertension. The SHR is the model that most closely matches the human hypertension, as it has similar characteristics, such as increased peripheral resistance, cardiac output and progressive left ventricular hypertrophy. Thus, female SHR may become a model of hypertension in menopause, very similar to that found in women. The aim of this study was to asses from which time of pre-menopausal period are significant changes in cardiovascular function of female SHR, independent of the absence of estrogenic activity. Cardiac electrical activity was assessed by electrocardiogram (ECG) performed in rats under anesthesia at the end of each month of age to determine the period in which we would observe the changes in excitation and cardiac electrical conduction become significantly different. From these results, theses animals were distributed into 3 groups (n=10) of study: 3, 6 and 12 month-old. It was also observed that female with 3 and 6 month old were cycling through the vaginal smear method. We determined the blood pressure and hemodynamic ventricular through catheterization of right femoral artery in anesthetized rats. With these results, we evaluated the systolic function (+dp/dt), contractility index (IC), diastolic function (-dp/dt) and complacency (tau) of left ventricle. Cardiac remodeling or hypertrophy was assessed by left ventricular morphometry. In addition, we assessed the Autonomic Nervous System activity on cardiac function through the heart rate variability analysis as an indicator of cardiovascular involvement. The young SHR (3 month old) showed a gradual and progressive increase since the beginning of the blood pressure according to the aging, when compared to Wistar rats of the same age. Such ageing effects were also observed in ECG study of SHR, which showed from 6 month-old, significant changes in the QRS, QT and QT interval durations and changes in the ECG morphology, with superposition of two R waves and T wave inversion, typical of cardiac ischemia, which are new results for this model. For ventricular hemodynamic parameters, there was an increased contractility index due to left ventricular hypertrophy from 6 month. Over time (12 month), this hypertrophy has become harmful because it was associated with reduce ventricular compliance, thereby damaging the lusitropic activity. Furthermore, data from heart rate variability indicated that, since 6 month-old tone sympathetic tone predominance on heart function associated with reduction of parasympathetic modulation, making these animals subjected to arrythmias. In conclusion, SHR showed from 6 month-old, significant cardiovascular changes that result in daley in transmission of cardiac electrical impulse, increased left ventricular overload and may result in cardiac arrithimias and sudden death, as prematurely observed by the of heart rate variability

ASSUNTO(S)

ratos espontaneamente hipertensos eletrocardiograma idade pressão arterial hipertrofia spontaneously hypertensive rats electrocardiogram aging blood pressure hypertrophy

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