Avaliação experimental do metabolismo energético em dois protocolos de sobrecarga sistólica do ventrículo direito / Experimental evaluation of energy metabolism in two right ventricle systolic overload protocols

AUTOR(ES)
FONTE

IBICT - Instituto Brasileiro de Informação em Ciência e Tecnologia

DATA DE PUBLICAÇÃO

16/03/2012

RESUMO

Objective: Altered energy metabolism has been identified in myocardial hypertrophy. Some processes are considered beneficial, whereas others are linked to heart failure. The purpose of this study was to compare the activity of three different energy metabolism enzymes in two different protocols of right ventricle (RV) systolic overload in young goats. Methods: 27 young goats were separated into three groups: Sham (no overload), Continuous (continuous systolic overload) and Intermittent (4 periods of 12-hour systolic overload, alternated with a 12-hour resting period). During a 96-hour protocol, systolic overload was adjusted to achieve a 0.7 RV / aortic pressure ratio. Echocardiographic and hemodynamic evaluations were performed before and after systolic overload every day postoperatively. After the study period, the animals were humanely killed for morphological and Glucose-6-phosphate dehydrogenase (G6PD), hexoquinase (HK) and lactate dehydrogenase (LDH) activity assessment. Results: There was a 92.1% and 46.5% increase in RV and septal masses of Intermittent group, respectively, as compared to Sham group, while Continuous systolic overload resulted in 37.2% increase of only septal mass. There was a small, but significant increase in water content in RV and septum of Intermittent and Continuous groups, as compared to Sham group (RV, p=0.0014; Septum, p=0.0004). At the end of protocol, it was observed a greater increase in RV thickness (103.8%) in Intermittent group, as compared to Continous group (38.4%). There was also a significant right ventricle dilatation in Continuos group along the protocol, as compared to the other groups (p<0.001). A worsening RV myocardial performance index occurred in the continuous group at 72 hours and 96 hours, compared with the sham (P<0.039) and intermittent groups (P<0.001). Compared to Sham, RV to LV G6PD activity ratio was elevated by 130.1% in Continuous group (p= 0,012) and by 39.8% in Intermittent group (p=0.764). The acute hypertrophic process in the RV did not altered the HK and LDH enzymatic activity among study groups. Conclusions: Despite of a proportional lesser exposure to systolic overload, intermittent pulmonary trunk banding promoted greater RV hypertrophy. This study indicates that continuous systolic overload for ventricle retraining causes upregulation and hyperactivity of myocardial G6PD. Since pentose phosphate pathway enhances cytosolic NADPH availability, this altered energy substrate metabolism can elevate levels of free radicals by NADPH oxidase, an important mechanism in the pathophysiology of heart failure. It suggests that Intermittent systolic overload may provide better results for 2-stage Jatene operation as compared to continuous protocol

ASSUNTO(S)

artéria pulmonar cabras cardiac surgical procedures goats heart ventricles hipertrofia ventricular direita hipertrofia/fisiopatologia hypertrophy/physiopathology procedimentos cirúrgicos cardíacos/métodos pulmonary artery right ventricular hypertrophy transposição dos grandes vasos/cirurgia transposition of the great vessels/surgery ventrículos cardíacos

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