[Spironolactone protection from hydralazine-induced stress in the rat myocardium]. / Protecção pela espironolactona do estresse pela hidralazina em miocárdio de ratos.

OBJECTIVES: We wished to verify the possible protective action of spironolactone (SPIRO), through its blocking action of slow calcium channels, in what concerns behavioural, morphologic, histochemical and ultrastructural alterations caused by experimental exposure to hydralazine (HZ), due to the excess release of catecholamines and the cellular influx of calcium. MATERIAL AND METHODS: Forty-eight adult male Wistar rats [correction of mice] were divided into 4 groups. The control group (CON) was administered olive oil for 4 days and distilled water i.v. on the last day, the hydralazine group (HZ) was administered olive oil for 4 days and 40 mg/kg i.v. of hydralazine on the last day; the spironolactone group (SPIRO) was administered 20 mg/kg of spironolactone diluted in olive oil for 4 days and distilled water on the last day; and the hydralazine with spironolactone group (HZ + SPIRO) was administered 20 mg/kg of spironolactone diluted in olive oil for 4 days and 40 mg/kg i.v. of hydralazine on the last day. The rats [correction of mice] were dissected and fragments of the myocardium removed for electron microscopy, and suprarenal fragments removed for light microscopy. Mitochondrial alterations characterised by ridge edema, lysis and vacuolisation (Cristolysis rate = damaged mitochondria/total mitochondria) were considered in the ultrastructural study. RESULTS: Light microscopy of the HZ group showed intense depletion of lipids in the cortical region of the suprarenals. The HZ + SPIRO group did not present significant alterations and was similar in appearance to the CON group. The ultrastructural study of the myocardium revealed the following rates of Cristolysis: CON group = 5.8%, HZ group = 91.9%, SPIRO group = 10.9%, HZ + SPIRO group = 10.2%*. (* = p < 0.001 chi-square test). CONCLUSION: The use of spironolactone in a model of stress induced by hydralazine caused: 1. Myocardial protection shown by reduced lesion of cardiomyocytes; 2. Protection of the suprarenals.

[Effect of verapamil on left ventricular hypertrophy induced by isoproterenol]. / Efeito do verapamil na hipertrofia ventricular esquerda induzida pelo isoproterenol.

PURPOSE: We evaluated whether verapamil (VERA) has a protective effect on left ventricular hypertrophy (LVH) induced by Isoproterenol (ISO) in rat. METHODS: Seventy two male adult rats were divided in four groups and treated accordingly during eight days: Control (CON), VERA (10 mg/kg), ISO (0.3 mg/kg) and VERA + ISO. It was measured in 10 animals from each group heart rate, blood pressure, left ventricle dry weight and ratio between left ventricular weight (LVW) and rat weight. Samples were taken from the left ventricle to be examined by light microscopy. RESULTS: LVW of the CON group was 0.145 g, of VERA was 0.144 g, of ISO with 0.201 g, and of VERA + ISO was 0.148 g. The difference between ISO group and others was statistically significant (P < 0.05). The LVW/W ratio also showed similar result. The myocardial pattern induced by ISO was left hypertrophy and collagen content increase. In VERA + ISO group it was found a protective effect to hypertrophy (ISO group 97% vs VERA + ISO 87%; p < 0.001) and increased collagen content. CONCLUSION: VERA prevents the deleterious effects of ISO in the myocardium. Probably this action is due to prevention the myocardial hypertrophy and proliferation of collagen tissue.