RUNNING PERFORMANCE AND CARDIOVASCULAR CAPACITY ARE NOT IMPAIRED IN CREATINE-DEPLETED RATS

Several published reports have indicated that derangement of the phosp hocreatine/creatine (Cr) energy-buffering system via Cr analogue feedi ng results in cardiomyopathy when cardiac performance is assessed in v itro. The present study was designed to examine indexes of cardiac per formance in rats that have been chronically Cr depleted. Adult (180 +/ - 4 g) rats were assigned to a normal diet (ND) (n = 8) or a Cr-deplet ion diet (CD) group (n = 10). After 61 +/- 1 days of ad libitum feedin g, measurements of steady-state exercise O-2 consumption were made. He modynamic indexes were then assessed during incremental running to pea k sustained levels. Rats were then killed and the left ventricle was e xcised. In the CD group Cr was depleted 82% and V-1 isomyosin decrease d while V-1 increased. O-2 consumption during steady-state running was not different in CD rats. The respiratory exchange ratios of CD rats reflected a bias toward fat utilization during the latter stages of pr olonged exercise. The exercise heart rates and peak systolic blood pre ssures of CD rats were slightly lower than those of ND rats. Both nega tive and positive rates of left ventricular pressure development were significantly reduced at all running speeds in the CD rats. CD rats we re capable of exercise performance equal to that of ND animals. The he modynamic and metabolic data suggest that the adaptations seen in the CD animals may be similar to those reported after endurance training. These results indicate that chronic Cr depletion does not impair eithe r the circulatory or exercise capacity of rodents.