Exercise performance in moderate hypoxia in rats with impaired carotid bodies

Abstract

Previous studies have shown a positive correlation between the magnitude of the resting hypoxic ventilatory response (HVR) and exercise performance at high altitude in humans. We employed a rodent model to experimentally test this relationship. Rats exposed to chronic hyperoxia during postnatal development exhibit smaller carotid bodies and reduced HVR as adults. Therefore, rats were exposed to 60% O2 for the first 2 postnatal weeks. At 2‐3 months of age, these rats were run on a treadmill at various work rates in both room air and moderate hypoxia (12% O2) to assess endurance (time to exhaustion at 20 m/min, 5° incline) and maximal rate of O2 consumption (VO2,max). Running times and VO2,max were reduced by hypoxia in both control and hyperoxia‐treated rats (P<0.001). In hypoxia, hyperoxia‐treated rats exhibited somewhat shorter times to exhaustion than controls (21±2 (SEM) vs. 29±2 min; P<0.01). In contrast, VO2,max during moderate hypoxia did not differ between treatment groups. Although HVR was not measured in this study, histology confirmed a significant reduction in carotid body volume in hyperoxia‐treated rats (P<0.01). We conclude that HVR and/or carotid body size may have modest effects on hypoxic exercise performance in rats. Supported by NIH grant P20 RR‐016463 (Maine INBRE).