Putrescine and 5-hydroxytryptamine accumulation in rat lung slices: cellular localization and responses to...

The cellular localization of putrescine (1,4-diaminobutane) and 5-hydroxytryptamine (5HT) following the accumulation of tritium-labeled putrescine (2.5 microM) or 5HT (0.5 microM) into rat lung slices was determined by autoradiography at the light microscope level. Putrescine labeling was found to occur in type II alveolar epithelial cells and in branchiolar nonciliated (Clara) cells, and possibly also in type I alveolar epithelial cells. The pattern of 5HT labeling was clearly different from that with putrescine, since the parenchyma was diffusely labeled with no preferential location in type II cells, but with strong labeling of the endothelium of large vessels and also the pleural mesothelium. The apparent kinetic parameters for the tissue uptake of [3H]putrescine (2.5 to 80 microM) and [14C]5HT (0.5 to 16 microM; both being simultaneously present in a 5 to 1 molar ratio) were studied in lung slices from normal rats and rats pretreated with O,S,S-trimethyl phosphorodithioate (OSSMe, 11 to 95 mg/kg, po), with paraquat (20 mg/kg, ip), or with alpha-naphthylthiourea (ANTU, 5 or 10 mg/kg, ip). OSSMe and paraquat were used as models for pulmonary epithelium-damaging agents, and ANTU was taken as a model for a pulmonary endothelium-damaging agent. The Vmax for the uptake of 5HT was significantly increased (without change in Km) following treatment with OSSMe and paraquat. Following ANTU treatment the Vmax for the uptake of 5HT was unchanged (5 mg/kg) or increased (10 mg/kg, Km also increased). These results indicate that in lung slices the response to lung injury may be associated with an increased accumulation of 5HT. The Vmax for the uptake of putrescine was significantly decreased (without change in Km) following treatment with OSSMe and paraquat. Following ANTU treatment the Vmax for the uptake of putrescine was unchanged (5 mg/kg) or decreased (10 mg/kg, no change in Km). These results suggest that a decreased putrescine uptake is a sensitive index of pulmonary epithelial damage.