AJP - Heart and Circulatory Physiology, Vol 243, Issue 4 536-H545, Copyright © 1982 by American Physiological Society
Adenosine's role in coronary vasodilation induced by atrial pacing and norepinephrine
J. P. Manfredi and H. V. Sparks Jr
If adenosine (ADO) mediates metabolic vasodilation in the heart, increases
in interstitial ADO (ISF[ADO]) must accompany increases in coronary
vascular conductance. We tested this using ADO release, defined as the
difference in [ADO] in coronary venous and arterial plasma multiplied by
coronary plasma flow, as an index of ISF[ADO]. Pentobarbital-anesthetized
dogs received intravenous norepinephrine or left atrial pacing, and the
resulting changes in coronary blood flow (delta CBF), conductance (delta
C), myocardial oxygen consumption (delta VO2), and ADO release (delta RADO)
were measured. If ISF[ADO] and C are coupled, the ratio delta RADO/delta C
should be greater than zero. For dogs receiving atrial pacing, the ratios
delta RADO/delta C, delta RADO/delta CBF, and delta RADO/delta VO2 equal
-2.4 +/- 2.2 nmol . mmHg-1 . ml-1, -0.022 +/- 0.020 nmol/ml, and -0.13 +/-
0.12 nmol/ml, respectively. These values do not differ from zero. For dogs
receiving norepinephrine, delta RADO/delta C, delta RADO/delta CBF, and
delta RADO/delta VO2 equal 9.7 +/- 1.8, 0.051 +/- 0.017, and 0.44 +/- 0.13,
respectively. These values are greater than zero (P less than 0.05). These
differences between atrial pacing and norepinephrine infusion rate observed
despite similar changes in C, CBF, and VO2. We conclude that ADO may
mediate the vasodilation induced by norepinephrine, but not atrial pacing.
