Deletion of CD73 increases exercise power in mice.

Ecto-5'-nucleotidase or CD73 is the main source of extracellular adenosine involved in the activation of adenosine A receptors, responsible for the ergogenic effects of caffeine. We now investigated the role of CD73 in exercise by comparing female wild-type (WT) and CD73 knockout (KO) mice in a treadmill-graded test to evaluate running power, oxygen uptake (V̇O), and respiratory exchange ratio (RER) - the gold standards characterizing physical performance. Spontaneous locomotion in the open field and submaximal running power and V̇O in the treadmill were similar between CD73-KO and WT mice; V̇Omax also demonstrated equivalent aerobic power, but CD73-KO mice displayed a 43.7 ± 4.2% larger critical power (large effect size, P < 0.05) and 3.8 ± 0.4% increase of maximum RER (small effect size, P < 0.05). Thus, KO of CD73 was ergogenic; i.e., it increased physical performance.