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Continued artificial selection for running endurance in rats is associated with improved lung function

¹Union College, Schenectady, New York; ²University of California-San Diego, La Jolla, California; ³University of Kansas Medical Center, Kansas City, Kansas; and ⁴University of Michigan, Ann Arbor, Michigan

Submitted 18 March 2008 ; accepted in final form 18 March 2009

Previous studies found that selection for endurance running in untrained rats produced distinct high (HCR) and low (LCR) capacity runners. Furthermore, despite weighing 14% less, 7th generation HCR rats achieved the same absolute maximal oxygen consumption (O_2max) as LCR due to muscle adaptations that improved oxygen extraction and use. However, there were no differences in cardiopulmonary function after seven generations of selection. If selection for increased endurance capacity continued, we hypothesized that due to the serial nature of oxygen delivery enhanced cardiopulmonary function would be required. In the present study, generation 15 rats selected for high and low endurance running capacity showed differences in pulmonary function. HCR, now 25% lighter than LCR, reached a 12% higher absolute O_2max than LCR, P < 0.05 (49% higher O_2max/kg). Despite the 25% difference in body size, both lung volume (at 20 cmH₂O airway pressure) and exercise diffusing capacity were similar in HCR and LCR. Lung volume of LCR lay on published mammalian allometrical relationships while that of HCR lay above that line. Alveolar ventilation at O_2max was 30% higher, P < 0.05 (78% higher, per kg), arterial PCO₂ was 4.5 mmHg (17%) lower, P < 0.05, while total pulmonary vascular resistance was (insignificantly) 5% lower (30% lower, per kg) in HCR. The smaller mass of HCR animals was due mostly to a smaller body frame rather than to a lower fat mass. These findings show that by generation 15, lung size in smaller HCR rats is not reduced in concert with their smaller body size, but has remained similar to that of LCR, supporting the hypothesis that continued selection for increased endurance capacity requires relatively larger lungs, supporting greater ventilation, gas exchange, and pulmonary vascular conductance.

pulmonary O₂ transport; lung diffusing capacity; lung volume; endurance capacity; genetic models

This article has been cited by other articles:

				R. A. Howlett, S. D. Kirkton, N. C. Gonzalez, H. E. Wagner, S. L. Britton, L. G. Koch, and P. D. Wagner Peripheral oxygen transport and utilization in rats following continued selective breeding for endurance running capacity J Appl Physiol, June 1, 2009; 106(6): 1819 - 1825. [Abstract] [Full Text] [PDF]