RESUMO
The main purpose of this study was to investigate the effects of short-term L-NAME treatment on the contractile function of left ventricle (LV) myocytes and the expression of proteins related to Ca(2+) homeostasis. Data from Wistar rats treated with L-NAME (L group, n = 20; 0.7 g/L in drinking water; 7 days) were compared with results from untreated controls (C group, n = 20). Cardiomyocytes from the L group showed increased (p < 0.05) fractional shortening (23%) and maximum rate of shortening (20%) compared with the C group. LV from the L group also showed increased (p < 0.05) expression of the ryanodine receptor 2 and Na(+)/Ca(2+) exchanger proteins (76% and 83%, respectively; p < 0.05). However, the L and C groups showed similar in vivo hemodynamic parameters of cardiac function. In conclusion, short-term NOS inhibition determines an increased expression of Ca(2+) regulatory proteins, which contributes to improving cardiomyocyte contractile function, preserving left ventricular function.
Assuntos
Ventrículos do Coração/efeitos dos fármacos , Miócitos Cardíacos/efeitos dos fármacos , NG-Nitroarginina Metil Éster/farmacologia , Óxido Nítrico Sintase/antagonistas & inibidores , Animais , Cálcio/metabolismo , Ventrículos do Coração/citologia , Ventrículos do Coração/enzimologia , Ventrículos do Coração/metabolismo , Hemodinâmica/efeitos dos fármacos , Masculino , Contração Miocárdica/efeitos dos fármacos , Miócitos Cardíacos/enzimologia , Miócitos Cardíacos/metabolismo , Óxido Nítrico Sintase/metabolismo , Ratos , Canal de Liberação de Cálcio do Receptor de Rianodina/genética , Trocador de Sódio e Cálcio/metabolismoRESUMO
BACKGROUND: Physical exercise induces hemodynamic stress. OBJECTIVE: To evaluate if voluntary running and forced running induced different levels of stress protein (Hsp72) in the myocardium of female Wistar rats. METHODS: Female rats were randomly assigned to the following groups: forced treadmill running group (FR; n= 6), voluntary running group (VR; n=6) and control group (C; n=6). VR group animals had free access to running wheels, and those from FR group underwent a running program on a treadmill (18 m/min, 60 min/day, 5 days/wk) for 8 weeks. Left ventricle (LV) and right ventricle (RV) fragments were collected at sacrifice, and the relative immunoblot contents of stress protein (Hsp72) were determined. RESULTS: VR animals ran on average 4.87 km/wk, and FR rats ran 4.88 km/wk. Animals from VR and FR groups had less body weight gain (p<0.05) than those from C group (81.67 +/- 11.95g vs 81.17 +/- 10.18g vs 111.50 +/- 2.26g, respectively). Heart weight/body weight ratio was not significantly different (p>0.05) among VR, FR and C groups (4.54 +/- 0.79 mg/g vs 4.94 +/- 0.89 mg/g vs 4.34 +/- 0.87 mg/g, respectively). FR group animals had levels of Hsp72 (p<0.05) higher than those from VR, both in LV (287.45 +/- 35.86 % vs 135.59 +/- 5.10 %, respectively) and RV (241.31 +/- 25.83 % vs 137.91 +/- 45.20 %, respectively). CONCLUSION: Voluntary running and forced running induced different levels of Hsp72 in the myocardium of female Wistar rats.