Rat Pleural Cell Populations: Effects of MMMF Inhalation on Cytokine mRNA Expression and Population Characteristics

Because of the known dangers of asbestiform fibres, many man-made mineral fibres (MMMF) are being manufactured as replacements. Among substitute products in use today glass wool and rock/slag wool are probably “safer” than chrysotile asbestos as shown by epidemiological studies (Simonato et al., 1987). However, little published human data exist for the refractory ceramic fibres developed to provide more efficient insulation particularly during high temperature uses. At present therefore, the biological activity of ceramic fibres may best be examined by cell culture and well-designed animal studies (Brown et al., 1990). Such experiments need to take into account the possibility that differing mechanisms may be responsible for fibrosis and cancer. Transport of fibres to the serosal sites of the pleura is also poorly documented and several routes, i.e. lymphatic, systemic, direct translocation have been proposed, but none have been firmly established. Indeed, the mode of action whereby inhalation of inorganic fibres leads to pathogenic changes in pleural tissues is unknown, although there is a widespread assumption that the macrophage plays a central role via various inflammatory processes in initiating these events.