DIRECT EFFECT OF TOBACCO-SMOKE ON THE INTRINSIC MECHANICAL-PROPERTIES OF CARDIAC-MUSCLE

The direct effects of tobacco smoke from Kentucky University Reference cigarettes on the mechanical performance of isolated rat left ventricular muscle preparations were examined. Experiments were carried out with preparations contracting isometrically 12 times per minute at 28°C while at the apex of the length tension curve. Under oxygenated conditions, tobacco smoke bubbled through the bath induced an initial negative inotropic response. With larger volumes of smoke, initial depression was followed by recovery toward control values. Late recovery was inhibited by first passing the tobacco smoke through a Cambridge filter. Tobacco smoke added prior to 60 min of hypoxia, followed by 30 min of reoxygenation, had a dose-dependent deleterious effect on muscle performance during hypoxia and subsequent reoxygenation. The deleterious effect of smoke during hypoxia could largely be prevented by first passing the tobacco smoke through a Cambridge filter. The nicotine present in tobacco smoke could not by itself account for the changes under oxygenated conditions or those seen during hypoxia and reoxygenation. It is concluded that the gaseous phase of tobacco smoke is responsible for the negative inotropic effect seen under oxygenated conditions. The action of the particulate phase of the smoke (which is blocked at least in part by the Cambridge filter) appears to be responsible for the partial recovery of mechanical performance under oxygenated conditions and the potent deleterious effects seen during hypoxia and reoxygenation. © 1979.