The effect of ketanserin on hypoxia-induced vasoconstriction in isolated lungs.

The pure and selective serotonin blocking agent ketanserin (5-HT2 receptor blocker) was used to evaluate a possible role for serotonin as a mediator of the pulmonary vasoconstrictor response to alveolar hypoxia. Isolated and ventilated lungs (FiO2 = 0.21) from rats were perfused at 310 degrees (K) with homologous blood at constant volume inflow, and pressor responses to standardized periods of ventilation hypoxia (FIO2 = 0.02) were recorded. Pressor responses to pulmonary arterial bolus-injections of serotonin were tested both before and after administration of ketanserin for comparison with the responses to hypoxia. We found that ketanserin in doses adequate to block the response to serotonin, had no effect on the pulmonary vasoconstrictor response to hypoxia.