Coronary blood flow in physically trained rats

Coronary blood flow was measured using labelled microspheres (15 micrometer diameter) in sedentary and endurance trained rats during hypoxaemic conditions designed to develop coronary dilatation (Pa,O2 6.0 to 6.7 kPa [45 to 60 mmHg]). Rats that were trained for 12 to 18 weeks (26.8 m per minute, 15% gradient, 1 hour per day) had a significantly greater coronary blood flow conductance (15.3 +/- 1.0 mm3.min-1.kPa-1 aortic diastolic pressure, n = 20) than sedentary animals (10.8 +/- 0.9, n = 19). Even though cardiac hypertrophy (17%) was found in the trained animals, this increase in perfused mass accounted for only one-third of the increase in total coronary blood flow. Thus, there was a greater coronary blood flow per unit mass of the myocardium in the trained rats.