Comparative histochemical investigation of the glutathione S-transferase placental form and gamma-glutamyltranspeptidase during N-nitrosobis(2-hydroxypropyl)amine-induced lung carcinogenesis in rats

Abstract

Immunohistochemical staining using anti-rat glutathione S-transferase placental form (GST-P) rabbit antibody and enzyme histochemical staining for gamma-glutamyltranspeptidase (gamma-GT) were investigated in lesions appearing during lung carcinogenesis induced by N-nitrosobis(2-hydroxypropyl)amine (BHP) in rats. Rats were given BHP at a concentration of 2000 p.p.m. in drinking water, and were killed after 12 weeks of BHP intake, after 12 weeks of BHP intake followed by 12 weeks of tap water intake or after 20 weeks of continuous BHP intake. It was found that bronchiolo-alveolar hyperplasias, adenomas, adenocarcinomas, squamous metaplasias and squamous cell carcinomas had been induced by BHP. All of the squamous metaplasias and squamous cell carcinomas were shown to stain with GST-P but not with gamma-GT. On the other hand, the hyperplasias, adenomas and adeno-carcinomas stained with gamma-GT to various degrees and in different areas, but did not stain with GST-P. The incidence of gamma-GT phenotype and the average percentage of gamma-GT-positive areas in hyperplasias and adenomas suggested that adenocarcinomas might develop from hyperplasias and adenomas. These results suggest that GST-P is a marker for squamous lesions while gamma-GT is a marker for adenomatous lesions in rat lung carcinogenesis. Furthermore, squamous metaplasias appear to be preneoplastic lesions of squamous cell carcinomas while gamma-GT-positive hyperplasias or adenomas are preneoplastic lesions of peripheral adenocarcinomas.