Effect of chronic cigarette smoke exposure on pulmonary vasomotion in beagle dogs

To study the effect of chronic cigarette smoke exposure on the resistive properties of the pulmonary vasculature, left lower lobes from 12 control beagles and 6 beagles who had smoked cigarettes (50 cigarettes/wk for 40 wk) were perfused in situ to measure the vascular pressure-flow relationship and the resistance of the three vascular segments with the arterial and venous occlusion technique. In control subjects the vascular resistance in the arterial, middle, and venous segments was 23, 36, and 41% of the total, respectively. The segmental distribution of vascular resistance was not significantly different in the cigarette smoke-exposed dogs, despite the fact that the absolute values were 30-40% less than that of the control group. The longitudinal distribution of resistance among the three vascular segments and their response to drugs were different in beagles than was previously found in mongrels. In all beagles the veins were considerably more reactive than arteries. Vasoconstriction with serotonin (5-HT) prostaglandin F2 alpha (PGF2 alpha), norepinephrine, histamine, and methacholine (M) infusion occurred predominantly in the veins. The effect of PGF2 alpha and 5-HT was totally different than that previously observed in mongrels in which the constriction was predominantly in the arteries. Chronic cigarette smoking reduced the basal pulmonary vascular resistance and attenuated the venoconstrictor response to 5-HT and M but potentiated the hypoxic pressor response of the microvessels.