Effect of Exercise on Fractional Extraction of Catecholamines by the Denervated Heart in Conscious Dogs.

Abstract

To examine the applicability of Halter's assumption to the denervated heart during exercise, we measured the concentrations of norepinephrine (NE) and epinephrine (E) in arterial and coronary sinus plasma in cardiac denervated dogs. As the level of exercise was increased from 0 (at rest) to 3, 6, and 12 km/h, fractional extraction (FE) of NE significantly decreased from 51 +/- 7 to 39 +/- 5, 34 +/- 6, and 30 +/- 5%, respectively. FE of E did not decrease at exercise (at rest, 57 +/- 10; 3 km/h, 60 +/- 9; 6 km/h, 60 +/- 5; and 12 km/h, 66 +/- 6%). There was no significant difference between FE of NE and E at rest and at 3 km/h, but FE of NE was significantly less than that of E with 6 and 12 km/h exercise. We conclude that FE of NE by the denervated heart decreases during exercise, and that FE of NE and E are approximately equal at rest and at mild exercise, but not at strenuous exercise.