Type II pneumocytes and Clara cells, both epithelial cells that possess an active uptake system for polyamines, have been identified as possible precursor cells of at least some types of lung tumours. In this study we have investigated whether human pulmonary tumours exhibit putrescine uptake. Lung slices from both tumoral tissue and non-tumoral tissue, obtained from patients undergoing surgery for lung cancer, were incubated with radiolabelled putrescine at both 37 degrees C and 4 degrees C. The accumulation of putrescine was evaluated by its apparent kinetic parameters, in the presence or absence of cystamine, and by autoradiography. The investigated tumoral tissue (six squamous carcinomas and five adenocarcinomas) did not show accumulation of putrescine above that attributable to simple diffusion, except for one adenocarcinoma. In this specimen autoradiography showed that the accumulation was not specifically associated with any particular cell type, but that practically every cell accumulated putrescine. We conclude that human pulmonary tumours do not accumulate polyamines in a manner similar to normal pulmonary epithelial cells.
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