A light microscopic technique based on alkaline phosphatase histochemistry was developed to specifically quantitate Type II cells in the intact rat lung. Lungs were fixed in 4% neutral-buffered formalin containing 0.25 M sucrose and embedded in glycol methacrylate. Two micron thick sections were mounted on glass microscope slides. Alkaline phospahtase activity was localized by using naphthol AS-BI phosphate as substrate in 0.125 M 2-amino-2-methyl-1-propanol buffer containing 0.625 mM MgCl2 (pH 8.9). Sections were counterstained with Harris hematoxylin. Type II cells were the only cell type in the alveolar region containing alkaline phosphatase activity, an observation that was confirmed by using electron microscopic histochemistry. By combining the alkaline phosphatase staining technique with standard morphometric procedures, the proliferative response to a single intratracheal dose of 10 mg silica was followed as a function of time. Type II cells were significantly increased at all time points examined. Twenty eight days following silica, Type II cells had increased to (252 ± 16) X 106 cells per set of lungs compared to a control value of (141 ± 32) X 166 cells. The method presented is a simple and rapid technique for examining Type II cell population kinetics.
ASJC Scopus subject areas
- Pulmonary and Respiratory Medicine
- Molecular Biology
- Clinical Biochemistry