Nicotine increases heart adenosine release, oxygen consumption, and contractility.

Area of Science:

• Pharmacology
• Cardiovascular Physiology
• Biochemistry

Background:

• Nicotine is a major component of tobacco smoke with known cardiovascular effects.
• Understanding nicotine's direct impact on cardiac function and metabolism is crucial.

Purpose of the Study:

• To investigate the effects of nicotine on cardiac contractility, oxygen consumption, and adenosine release in isolated perfused rat hearts.
• To determine if these effects are mediated by beta-adrenergic or muscarinic receptors.

Main Methods:

• Perfused rat hearts were exposed to varying concentrations of nicotine.
• Measurements included left ventricular pressure (LVP), maximal rates of pressure development/relaxation (+/- dP/dtmax), oxygen consumption, and coronary effluent adenosine levels.
• The role of beta-adrenergic and muscarinic receptors was assessed using propranolol and atropine.

Main Results:

• Nicotine caused a dose-dependent, sustained increase in LVP, +dP/dtmax, and -dP/dtmax.
• Cardiac oxygen consumption and coronary adenosine levels significantly increased with nicotine exposure.
• These effects were not altered by propranolol or atropine, indicating independence from beta-adrenergic and muscarinic pathways.
• Nicotine did not affect [14C]adenosine uptake by the heart.

Conclusions:

• Nicotine augments cardiac contractility and oxygen consumption independently of beta-adrenergic or muscarinic signaling.
• Nicotine elevates coronary adenosine levels, likely through enhanced myocardial production of adenosine.