567 Melting and boiling point: Tm=-92°C,Tb=-19°C Autoignition temperature: 300 °C Henry's law constant at 25°C H: 0,034 Pa*m3/mol TOXICOKINETICS The toxicokinetics of formaldehyde after inhalation, oral, or dermal exposure has been reported in several species by many investigators. The toxicokinetics in all of the animals studied is similar across species lines. Formaldehyde is an essential metabolic intermediate in all cells. It is produced during the normal metabolism of serine, glycine, methionine, and choline and also by the demethylation of N-, S-, and O-methyl compounds. After oxidation of formaldehyde to formate, the carbon atom is further oxidized to carbon dioxide (CO2) or incorporated into purines, thymidine, and amino acids via tetrahydrofolatedependent one-carbon biosynthetic pathways. Exogenous formaldehyde appears to be readily absorbed from the respiratory and gastrointestinal tracts, but poorly absorbed following dermal application
cells (Allen and Goll 2003). Ultrastructural including animals, plants, fungi, and bacteria. studies indicate lysosomes are prevalent in Discovered about a decade after cathepsins fetal muscle tissue but occur much less fre- (Guroff 1964), calpains have been exten- quently in adult skeletal muscle. Cathepsins sively researched and the subject of many are distinguished by their active sites (aspar- reviews on muscle proteolysis (Goll et al. tic, cysteine, and serine proteases) and 1992, 1998, 2003; Geesink et al. 2000; Ilian substrate specificity. Over 15 lysosomal et al. 2001; Friedrich and Bozóky 2005; cathepsins have been identified, but only Geesink et al. 2005; Koohmaraie and Geesink eight (B, L, H, S, F, K, D, E) have been found 2006; Geesink and Veiseth 2009). Currently, in skeletal muscle fibers (Barnier 1995; at least 15 different calpains have been iden-
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