Altered enzyme expression in propylnitrosamine-induced Syrian hamster lung lesions.

Focal proliferative and neoplastic lung lesions induced in Syrian hamsters by dihydroxy-di-n-propylnitrosamine (DHPN) were investigated using a combined histochemical, autoradiographic and electron microscopic approach. Expression of elevated glucose-6-phosphate dehydrogenase (G6PD) and gammaglutamyl-transpeptidase (GGT) activities and levels of immunohistochemically demonstrable glutathione S-transferase placental form (GST-P) were evident in epithelial cells of focal proliferative populations and bronchioloalveolar neoplasms. Binding for the GST-C form, normally only weak, became very pronounced in the stromal elements of DHPN-induced lesions. Increased labelling with tritiated thymidine was associated with increase in morphological atypia within the tumours. Although the enzyme phenotype findings were equivocal the presence of lamellar bodies in some cells of focal proliferative and neoplastic lesions suggested an origin from alveolar type II cells. The present results regarding changed enzyme phenotype in lung lesions suggest important similarities at the biochemical level for the process of neoplasia in the different target organs of DHPN in the hamster and indicate that GST-P may be a useful 'marker' for lung neoplasia.