Cellular localization of metallothionein in the lung following repeated cadmium inhalation

Cadmium and metallothionein (MT) levels were measured in lungs derived from Lewis rats exposed 0, 5, 10, 15, 20, 24, or 30 times to a Cd acetate aerosol (1.6 mg/m3). Cd burden rose from 2.21 micrograms in control lungs to 42.55 micrograms in lungs of animals exposed 30 times to the Cd aerosol. Pulmonary MT, expressed as nmoles Cd-thionein, paralleled Cd retention. Levels increased from 7.5 nmol in control animals to a value of 340.5 nmol in animals exposed 30 times to Cd. Energy dispersive X-ray microanalysis and the laser micro-probe analyzer were used to localize Cd within the lung. Lung tissue was prepared by a variety of chemical and physical fixation procedures. Cd localization proved unsuccessful by these techniques, presumably because the cellular Cd levels were below the limits of detectability. Using a immunohistochemical procedure which employed an antibody to MT, pulmonary MT was found in alveolar epithelial cells, fibroblasts, and lymphocytes. The MT was restricted to the nuclei of these cells.