Effects of nicotine on heart dimensions and blood volume in male and female rats

The adverse effects of tobacco smoking on the cardiovascular system are well established. Effects of nicotine on the heart, in contrast, are not well characterized. Understanding specific effects of nicotine on the heart and on blood volume is relevant to (a) elucidating the mechanisms by which nicotine may contribute to heart disease and (b) determining potential risks associated with nicotine products used in smoking cessation or to treat various medical conditions. The present experiment investigated effects of continuous nicotine administration for 14 days (0, 6, or 12 mg/kg/day) on heart histopathology and blood volume (a measure of hemoconcentration) in 59 male and 59 female rats of two strains (Sprague-Dawley and Long-Evans). Following nicotine administration, animals were sacrificed and blood volume was measured. Heart length; heart weight; left ventricle, right ventricle, lateral wall, anterior wall, and posterior wall thicknesses; and intraventricular width (i.e., septum) were measured. Nicotine reduced heart weight, heart length, and overall blood volume. Females were more sensitive than males to the effects of nicotine on heart weight. In contrast, males were more sensitive than females to the effects of nicotine on heart length. Together, these findings suggest that males and females differ in their sensitivity to nicotine's cardiac effects.