Skeletal and respiratory muscle blood flow redistribution during submaximal exercise in pulmonary hypertensive rats

Pulmonary hypertension (PH) is a chronic, progressive disease characterized by pulmonary vascular remodelling, dyspnoea and exercise intolerance. Key facets of dyspnoea and exercise intolerance include skeletal and respiratory muscle contractile and metabolic disturbances; however, muscle perfusion during exercise has not been investigated. We hypothesized that diaphragm blood flow ( ) would be increased and locomotory muscle would be decreased during submaximal treadmill running in PH rats compared to healthy controls. Female Sprague-Dawley rats were injected (i.p.) with monocrotaline to induce PH (n = 16), or a vehicle control (n = 15). Disease progression was monitored via echocardiography. When moderate disease severity was confirmed, maximal oxygen uptake ( ) tests were performed. Rats were given >24 h to recover, and then fluorescent microspheres were infused during treadmill running (20 m/min, 10% grade; ∼40-50% maximal speed attained during the test) to determine tissue . In PH rats compared with healthy controls, was lower (84 (7) vs. 67 (11) ml/min/kg; P