AJP - Endocrinology and Metabolism, Vol 243, Issue 1 52-E58, Copyright © 1982 by American Physiological Society
Cardiac uptake and secretion of catecholamines during adrenergic stimulation in vivo
J. B. Halter, K. O. Kelley and K. L. Gould
Cardiac uptake and secretion of epinephrine (Epi) and norepinephrine (NE)
were studied at rest and during the response to systemic vasodilation with
dipyridamole in conscious dogs. Chronically implanted catheters in the left
atrium and anterior great coronary vein allowed simultaneous measurement of
arterial and venous levels of NE and Epi across the segment of myocardium
perfused by the left anterior descending coronary artery. Arterial Epi was
greater than coronary venous Epi both at rest and during vasodilation.
Arterial and venous NE levels were similar at rest. However, arterial NE
rose more than venous NE during dipyridamole. Thus, there was net cardiac
uptake of NE as well as Epi when systemic plasma catecholamine levels
increased in response to vasodilation. Fractional extraction [(A-V)/A X
100)] of Epi by the heart was 50% and was not affected over a sevenfold
range of coronary artery flow. Fractional extraction of NE (5-15%) was
significantly lower than that of Epi, most likely due to cardiac secretion
of NE. Cardiac NE secretion was estimated to increase fourfold during
dipyridamole. Thus, cardiac tissue of trained dogs avidly takes up
circulating catecholamines. Despite an apparent increase of NE secretion by
the heart during the systemic adrenergic response to dipyridamole, the
heart remained an organ of net NE uptake and therefore did not contribute
to the observed increase of systemic NE levels.
