The effect of nicotine on adenosine release, oxygen consumption, and contractility was investigated in perfused rat hearts. Continuous infusion of nicotine into the perfusing physiological saline (PS) elicited a propranolol (10(-6) M) sensitive transient elevation of developed left ventricular pressure (LVP) and maximum rates of left ventricular pressure development and relaxation (+/- dP/dtmax) within 20 s, which subsequently declined to maintained elevated plateau levels by 1 min. The continuous infusions of nicotine to achieve PS concentrations of 5 X 10(-4), 1 X 10(-4), or 5 X 10(-5) M, respectively resulted in significant increases in the mean plateau levels of LVP (33.4, 10.1, or 6.3%), +dP/dtmax (26.3, 10.8, or 6.9%) and-dP/dtmax (35.0, 11.9, or 9.0%) at 1 min. The inclusion of propranolol (10(-6) M) with or without atropine (10(-6) M) did not alter these maintained plateau responses to nicotine. During the plateau phase of the contractile response oxygen consumption of the hearts was significantly elevated by 36, 19, or 11%, and mean levels for adenosine in the coronary effluent rose by 261, 76, or 74% in response to 5 X 10(-4), 1 X 10(-4), or 5 X 10(-5) M nicotine, respectively. Nicotine did not influence [14C]adenosine uptake by the hearts. These results suggest that nicotine is capable of 1) augmenting cardiac contractility and oxygen consumption independent of beta-adrenergic or muscarinic influence, and 2) elevating the appearance of adenosine in the coronary circulation presumably by enhancing myocardial production of the nucleoside.
Myocardial oxygen consumption and the left ventricular pressure-volume area in normal and hypertrophic canine hearts.
