Cardiac adaptation to endurance exercise in rats

Abstract

Endurance exercise is widely assumed to improve cardiac function in humans. This project has determined cardiac function following endurance exercise for 6 (n = 30) or 12 (n = 25) weeks in male Wistar rats (8 weeks old). The exercise protocol was 30 min/day at 0.8 km/h for 5 days/week with an endurance test on the 6th day by running at 1.2 km/h until exhaustion. Exercise endurance increased by 318% after 6 weeks and 609% after 12 weeks. Heart weight/kg body weight increased by 10.2% after 6 weeks and 24.1% after 12 weeks. Echocardiography after 12 weeks showed increases in left ventricular internal diameter in diastole (6.39 ᠰ.32 to 7.90 ᠰ.17 mm), systolic volume (49 ᠷ to 83 ᠱ1 嬩 and cardiac output (75 ᠳ to 107 ᠸ ml/min) but not left wall thickness in diastole (1.74 ᠰ.07 to 1.80 ᠰ.06 mm). Isolated Langendorff hearts from trained rats displayed decreased left ventricular myocardial stiffness (22 ᠱ.1 to 19.1 ᠰ.3) and reduced purine efflux during pacing-induced workload increases. 31P-NMR spectroscopy in isolated hearts from trained rats showed decreased PCr and PCr/ATP ratios with increased creatine, AMP and ADP concentrations. Thus, this endurance exercise protocol resulted in physiological hypertrophy while maintaining or improving cardiac function. (Mol Cell Biochem 251: 51-59, 2003)