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Cardiac and renal antioxidant enzymes and effects of tempol in hyperthyroid rats

²Facultad de Medicina, Departamento de Fisiología y ¹Servicio de Nefrología, Unidad Experimental, Hospital Virgen de las Nieves, Granada; and ³Departamento de Ciencias de la Salud, Universidad de Jaén, Jaén, Spain

Submitted 27 December 2004 ; accepted in final form 31 May 2005

This study evaluated the activity of cardiac and renal antioxidant enzymes [superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX), and glutathione reductase (GR)] and whether chronic treatment with tempol, a cell membrane-permeable SOD mimetic, ameliorates the hypertension of hyperthyroidism. Two experiments were performed. In experiment I, the following four groups of male Wistar rats were used: control group and three groups that received thyroxine (T₄) at 10, 50, or 75 µg·rat^–1·day^–1. In experiment II, tempol was orally administered (18 mg·kg^–1·day^–1) to control and T₄-treated (75 µg·rat^–1·day^–1) rats. All treatments were maintained for 6 wk. Body weight, tail systolic blood pressure (BP), and heart rate were measured one time a week, and direct BP and morphological, metabolic, plasma, and renal variables were measured at the end of the experiment. Enzymatic activities were measured in renal cortex and medulla and right and left ventricles. In renal cortex, SOD activity was decreased in the T₄-75 group, and there was a dose-related increase in CAT activity and decrease in GPX and GR activities in T₄-treated groups. Activity of all antioxidant enzymes was reduced in left ventricle in T₄-50 and T₄-75 groups and in right ventricle in the T₄-75 group. Tempol reduced BP, plasma malondialdehyde, and total urinary excretion of F₂ isoprostanes in hypertensive hyperthyroid rats but not in controls. Tempol did not improve cardiac hypertrophy, proteinuria, or creatinine clearance in hyperthyroid rats. In conclusion, the results obtained indicate that the activity of SOD, GPX, and GR in renal and cardiac tissues is decreased in hyperthyroidism and that antioxidant treatment with tempol ameliorates T₄-induced hypertension.

hyperthyroidism; hypertension; tempol; antioxidant enzymes; oxidative stress.

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