DIETARY-SODIUM-INDUCED CARDIAC REMODELING IN SPONTANEOUSLY HYPERTENSIVE RAT VERSUS WISTAR-KYOTO RAT

Objective. To study the effects of short-term and longterm high sodium intake on cardiac mass and design in sodium-sensitive spontaneously h ypertensive rats versus sodium-resistant Wistar-Kyoto rats. Methods. Y oung spontaneously hypertensive rats and Wistar-Kyoto rats were random ly allocated to control diet, 2 or 8% dietary sodium for 2-12 weeks an d changes in resting hemodynamics, cardiac angiotensin II level, sympa thetic activity and cardiac structure evaluated. Sympathetic activity was assessed by measuring levels of plasma catecholamines, responses o f blood pressure to ganglionic blockade, and rates of cardiac turnover of norepinephrine. Results. High sodium intake for 4 weeks increased left ventricle weight of Wistar-Kyoto rats aged 4 weeks (by 11 and 25% for 2 and 8% NaCl diets, respectively). This hypertrophic response wa s temporary, however, had already diminished after 6 weeks, and was ab sent after 12 weeks of a high sodium intake. However, after prolonged exposure concentric remodeling occurred (i.e. left ventricle wall thic kness:radius ratio increased with no change in left ventricle mass). H igh sodium intake did not affect resting blood pressure, cardiac index , cardiac angiotensin II level, and general sympathetic activity of Wi star-Kyoto rats. Short-term high sodium intake did not increase left v entricle mass of young spontaneously hypertensive rats, unless sodium intake was so high (8% NaCl) that blood pressure and general sympathet ic activity increased, too. However, a prolonged moderate (2%) increas e in sodium intake also caused concentric remodeling in spontaneously hypertensive rats without increasing left ventricle mass, blood pressu re, cardiac index, and general and cardiac sympathetic activities. Con clusions. The blood pressure in young Wistar-Kyoto rats is sodium-inse nsitive but the heart structure is sodium-sensitive and high dietary s odium intake causes an early hypertrophic response, and then concentri c remodeling. In contrast, hypertrophic response appears to occur afte r the response of blood pressure in spontaneously hypertensive rats, w hereas the remodeling is similar to that in Wistar-Kyoto rats. (C) 199 8 Lippincott-Raven Publishers.