The accumulation and localisation of putrescine, spermidine, spermine and paraquat in the rat lung: In vitro and in vivo studies

Abstract

Putrescine was accumulated into the isolated perfused rat lung by a temperature dependent process. The uptake obeyed saturation kinetics for which an apparent K m of 14 μM and V max of 48 nmol/g wet wt/hr was derived. After rats were dosed subcutaneously with [ 14C]putrescine, it was accumulated in the lung to concentrations greater than that in the plasma with the highest amount found between 3 and 12 hr. From 3 hr after dosing until 24 hr, there was a progressive increase in 14C label incorporated into spermidine, indicating that putrescine was converted to spermidine. Using autoradiographic techniques in lung slices the [ 3H]oligoamines were found in the alveolar epithelial type II, Clara and very probably the alveolar type I cells. With [ 3H]paraquat, the presence was detected only in the alveolar type II cells. Likewise, in the isolated perfused rat lung or following s.c. dosing of rats with [ 3H]putrescine the radiolabel was located only in the alveolar type II cell. We have suggested that the most likely explanation for the differences in localisation of label between in vitro and in vivo studies resulted from the use of [ 3H] label of different specific activity. Consequently we have concluded that the cell types with the ability of accumulate paraquat and oligoamines were the alveolar epithelial type I and type II cells and Clara cells.