Endothelium-dependent and -independent vasodilation and reactive hyperemia in healthy smokers.
Although cigarette smoking elicits a transient increase in peripheral vascular resistance in humans, the basal blood pressure (BP) is usually slightly lower in smokers. We hypothesized that this may be due to a compensatory increase in sensitivity in smokers to endogenous vasodilators. To test this, we studied endothelium-dependent and -independent vasodilator responses, and reactive hyperemia (RH) in the forearm of 25 healthy subjects [11 smokers (S) and 14 nonsmokers (NS)]. Endothelium-dependent vasodilation was induced by infusion into a brachial artery of stepwise increasing dosages of acetylcholine (ACh, 10-60 micrograms/kg/min) and endothelium-independent vasodilation by a similar infusion of nitroprusside (N, 1-6 micrograms/kg/min). RH was induced by release of a 5-min upper arm arterial occlusion. Forearm blood flow (FBF) was recorded by plethysmography. Endothelium-dependent vasodilation was more pronounced in S than in NS (p < 0.01), the maximal FBF during infusion of ACh being 20 +/- 6 and 14 +/- 4 ml/100 ml/min, respectively. Endothelium-independent vasodilation was also larger in S than in NS (p < 0.001), the maximal FBF during infusion of N being 14 +/- 3 and 12 +/- 2 ml/100 ml/min, respectively. ACh-induced vasodilator responses in S and NS were completely blocked by atropine. They were not decreased by trimethaphan, a nicotinic receptor inhibitor. RH was slightly more pronounced in S than in NS (p < 0.02), the postocclusive FBF 15 s after release of the occlusion being 25 +/- 4 and 21 +/- 3 ml/100 ml/min, respectively We propose that cigarette smoking increases the sensitivity of the vascular smooth muscle to vasodilator stimuli.
D000109:Acetylcholine / Q000494:pharmacology; D000328:Adult; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D004730:Endothelium, Vascular / Q000187:drug effects / Q000502:physiology*; D005260:Female; D005542:Forearm / Q000098:blood supply*; D006801:Humans; D008297:Male; D009599:Nitroprusside / Q000494:pharmacology; D012039:Regional Blood Flow / Q000187:drug effects; D012907:Smoking; D014655:Vascular Resistance / Q000187:drug effects; D014664:Vasodilation / Q000187:drug effects
D009599:Nitroprusside; D000109:Acetylcholine