Magnetometric evaluation for the effects of silicon carbide whiskers on alveolar macrophages.

Alveolar macrophages are thought to play an important role in fibrogenesis in the lungs caused by various types of exposure to dust. In this experiment, we evaluated the effect of silicon carbide whiskers (SiC) on alveolar macrophages mainly by unique magnetometry and also by established methods such as lactate dehydrogenase (LDH) activity, apoptosis measurement and morphological observations. Alveolar macrophages obtained from Syrian golden hamsters by bronchoalveolar lavages were exposed in vitro to Fe3O4 for 18 hours as an indicator for magnetometry and SiC for experiments. A rapid decrease of the remanent magnetic field, so called "relaxation", was observed after cessation of an external magnetic field in macrophages phagocytizing Fe3O4 alone, while relaxation was delayed in those concurrently exposed to SiC. Release of LDH from SiC-exposed macrophages into the medium was not significantly higher than the controls, but it increased dose-dependently. Apoptosis was recognized in macrophages exposed to 60 micrograms/ml of SiC by the DNA ladder detection method and morphological observations. Electron microscopic examination revealed irregular forms of nuclei and organellas in macrophages exposed to SiC. Magnetometry, LDH release and electron microscopic observation indicated mild cytotoxicity of SiC to alveolar macrophages.