THE EFFECTS OF VOLUNTARY RUNNING ON CARDIAC MASS AND AORTIC COMPLIANCE IN WISTAR-KYOTO AND SPONTANEOUSLY HYPERTENSIVE RATS

Objective To investigate the effects of voluntary running exercise fro m 4-20 weeks of age on aortic compliance in Wistar-Kyoto (WKY) rats an d spontaneously hypertensive rats (SHR). Design For each species we ma de comparisons between rats housed with an exercise wheel locked (10 r ats) and unlocked (10 rats). Methods Rats were killed using CO, asphyx ia and the aorta and heart of each rat were rapidly removed. The heart was dissected and weighed. A 4 mm descending proximal aortic ring was mounted on wires in an organ bath for determination of static complia nce from the slope of the diameter-pressure relationship derived using Laplace's equation. Results During the final 2 weeks of training WKY rats ran an average of 7.9 +/- 1.0 km/24 h compared with 1.0 +/- 0.2 k m/24 h for SHR. Body weights of WKY rats and SHR and of animals housed with locked and unlocked exercise wheels did not differ. The septum, left ventricle and total heart weights and left ventricular:body weigh t ratios of sedentary SHR were greater than those of sedentary WKY rat s. Trained WKY rats had significantly higher atrial, left and right ve ntricular and total heart weights and left ventricular:body weight rat ios than did untrained WKY rats. Aortic compliance was higher in train ed than it was in sedentary WKY rats (12.3 +/- 0.4 versus 14.2 +/- 0.5 mu m/mmHg, P< 0.05). There was no difference between heart weights an d aortic compliances of SHR housed with exercise wheels locked and unl ocked. Conclusion Exercise-trained WKY rats had greater intrinsic aort ic compliance when it was measured statically in vitro, which supports results of previous human work revealing a blood-pressure-independent component in the elevation of arterial compliance with training. The lower physical activity of the SHR strain used in this study could con tribute to their higher blood pressures and lack of change in aortic c ompliance with exercise training, (C) 1998 Rapid Science Ltd.