Since alveolar macrophages play an important role in the clearance of inhaled dust from air-ways, these cells have been used as a target for various toxic chemicals. Alveolar macrophages obtained from bronchoalveolar lavage of Syrian golden hamsters were concurrently exposed in vitro to Fe(3)O(4), as an indicator for magnetometry, and various concentrations of cadmium oxide (CdO) in this study. A rapid decrease of the remnant magnetic field, called relaxation, was observed after the cessation of an external magnetic field stimulus in macrophages concurrently exposed to phosphate-buffered saline or CdO at 0.1 microg/ml, while relaxation was delayed in those concurrently exposed to 1, 25, or 50 microg/ml CdO. Therefore, the concentration of CdO affecting relaxation in vitro was estimated at between 0.1 and 1 microg/ml. Release of LDH activity from CdO-exposed macrophages into the medium significantly increased at levels of 25 and 50 microg/ml CdO. Apoptosis was not detected in macrophages exposed to CdO by the DNA ladder detection method or morphological observations. Electron-microscopic examination revealed severe membrane damage and vacuolar changes in macrophages exposed to CdO. Since delayed relaxation is thought to occur by (1). disrupted cytoskeleton-driven random rotation of phagosomes containing iron oxide particles, (2). significant lactate dehydrogenase (LDH) activity release, and (3). detachment of cell membranes, CdO is considered to affect macrophage functions.