INHALED CIGARETTE-SMOKE SELECTIVELY REVERSES HUMAN HYPOXIC VASOCONSTRICTION

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