INHALED CIGARETTE-SMOKE SELECTIVELY REVERSES HUMAN HYPOXIC VASOCONSTRICTION

The acute effects of the inhaled gas phase of cigarette smoke on pulmonary (PAP) and systemic (SAP) arterial pressures and on plasma arterial cGMP content were compared with those of inhaling 10, 20 and 80 ppm nitric oxide (NO) in one healthy adult volunteer spontaneously breathing a hypoxic gas mixture. Hypoxia (FIO2 0.12) induced a sustained, stable pulmonary vasoconstriction. Inhaled NO induced a dose-dependent fall in PAP; plasma cGMP rose from 39.4 (hypoxia) to 164 pmol/ml (hypoxia plus 80 ppm NO). Exposure to cigarette smoke induced a rapid, consistent and reversible fall in PAP; plasma cGMP rose from 45.5 (hypoxia) to 138 pmol/ml (hypoxia plus cigarette smoke). Neither NO nor cigarette smoke inhalation induced any change in SAP. These data suggest that exposure to cigarette smoke is able selectively to reverse acute hypoxic vasoconstriction in humans without causing systemic vasodilation, an effect likely mediated through the NO-cCMP pathway.