Alteration of cardiovascular function in trained rats fed with fish oil

In vivo cardiovascular function of sedentary and exercise-trained rats were studied after a 3 week feeding period of diets containing either 10% fish oil, sunflower oil or lard. Rats were randomly assigned to six groups: fish oil diet: sedentary (FS), exercise-trained (FT); sunflower oil diet: sedentary (SS), exercise-trained (ST); lard diet: sedentary (LS), exercise-trained (LT). The exercised rats ran on a treadmill at a speed of 16 m/min, for 60 min/d, 7 days/week during 3 weeks. There was no significant difference in body weights and heart weights among the 6 groups at the end of the study. Heart function was evaluated in closed-chest rats after catheterization of the left ventricle with an ultraminiature catheter pressure transducer. Cardiovascular function of trained rats fed on fish oil diet was significantly different from that of other rats studied (FS, SS, ST, LS, LT). There was a 20% reduction in left ventricular systolic pressure (LVSP), LVdP/dt(max), mean aortic pressure (MAP), heart rate (HR) and a 30% reduction in LVdP/dt(min). We conclude that fish oil diet might induce a change in hemodynamic parameters only when associated with stress, such as the moderate exercise protocol in our experiments.