PULMONARY INACTIVATION OF 5‐HYDROXYTRYPTAMINE IS DECREASED DURING CIGARETTE SMOKE VENTILATION OF RAT ISOLATED LUNGS

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Abstract
The effect of cigarette smoke ventilation on the inactivation of [14C]‐5‐hydroxytryptamine (5‐HT) was studied in isolated perfused lungs of the rat. [14C]‐5‐HT 9.6 nmol was infused into the pulmonary circulation of rat lungs in 3 min. The nonrecirculating perfusion effluent was collected during the 5‐HT infusion in three consecutive 1 min fractions. The amount of metabolites of 5‐HT was determined from the perfusion effluent and from the perfused lungs. The amount of metabolites of 5‐HT in the perfusion effluent was decreased during cigarette smoke ventilation. The amount of metabolites of 5‐HT in the perfused lungs was also decreased by cigarette smoke ventilation, although the total amount of radioactivity in the lung tissue was not significantly changed. The decreased pulmonary inactivation of 5‐HT may cause increased circulating levels of 5‐HT, which would explain some cardiovascular changes during smoking.