An ultrastructural investigation of urethane-induced lung tumors in strain-A mice

Abstract

The cellular origin of chemically-induced lung tumors in mice has not been completely resolved. Brooks (1968) reported that most urethane-induced lung tumors in strain A mice were derived from type II alveolar epithelial cells. In contrast, Kauffman (1981) observed that the majority of clinically- induced lung tumor in Swiss mice were derived from Clara cells of the bronchiolar epithelium. Preliminary results from the present study are in agreement with those of Kauffman (1981) in that most urethane-induced lung tumors in strain A/J mice appear to be derived from Clara cells.Eight week-old female A/J mice were injected I.P. with 1000 mg/kg of urethane. Twelve months after injection, the mice were sacrificed by cervical dislocation and their lungs fixed in buffered 4% formalin - 1% glutaraldehyde, introduced via the trachea. Tumors in the right lung were identified grossly, catagorized according to size (<1-.5, 1.6-5, and >5 mm in diameter) and location (centrolobular or peripheral), and prepared for both light and electron microscopy.