An assessment of asbestos body formation in extrapulmonary sites: liver and spleen

Asbestos bodies (ABs) form as asbestos fibers become coated by a cellular iron- and protein-rich matrix. ABs have been reported in lymph nodes and a few extrapulmonary sites, but no data exist as to their formation outside of the lung. It is not clear whether the AB found in these extrapulmonary areas have been transported as mature structures from the lung or formed at the extrapulmonary site. This study was designed to determine if ABs are produced in extrapulmonary sites. The guinea pig efficiently forms ferruginous bodies in the lung and so it was chosen as a model to test the coating efficiency of amosite asbestos fibers in lung, liver and spleen.

Sized amosite asbestos (5 mg) was administered either endotracheally into lung (n = 2) or directly into liver (n = 4) and spleen (n = 4) of healthy 10-week-old male guinea pigs. The lung, liver and splenic tissues were removed at 40 and 180 days post inoculation and were examined histologically for the presence of AB via light microscopy. Uncoated fibers isolated from the tissues were characterized by electron microscopy. The coating efficiency was calculated as a ratio of uncoated/coated fibers per organ.

The coating efficiency ratios of fibers that were collected at 40 days post-injection from the individual sites were: lung - 350:1, liver - 4200:1, and spleen - 220,000:1. At 6 months post-injection the ratios for the individual sites consisted of: lung - 176:1, liver - 11,000:1, and spleen - 1000:1.

This study indicates that AB can be formed in extrapulmonary sites and that the coating efficiency in the lung is much greater than that within the liver or spleen.