Contribution of serum and cellular semicarbazide-sensitive amine oxidase to amine metabolism and cardiovascular toxicity

Semicarbazide-sensitive amine oxidase (SSAO) plays a role in the in vivo an d in vitro toxicity of several environmental and endogenous amines. We inve stigated the role of SSAO as a component of cell culture medium (through ad dition of fetal calf serum (FCS)) compared to intracellular SSAO in the in vitro cytotoxicity of three amines and metabolites. Smooth muscle cells and beating cardiac myocytes were grown in 96-well plates and exposed to vario us concentrations and combinations of FCS in medium, amines (allylamine, AA ; benzylamine, BZA; and methylamine, MA), and amine metabolites (aldehydes: acrolein, benzaldehyde, and formaldehyde; hydrogen peroxide, H2O2 ammonia, NH,). Amine and amine metabolite cytotoxicity was quantified by monitoring cell viability, SSAO activity was measured in FCS, cardiovascular cells, o r rat plasma by a radioenzymatic assay using [C-14]BZA. Our data show that AA and its aldehyde metabolite, acrolein, were the most toxic compounds to both cell types. However, AA toxicity was FCS-dependent in both cell types, while BZA, MA, and amine metabolite (i.e., aldehydes, H2O2, and NH,) cytot oxicity showed little FCS dependence. In these experiments, medium containi ng 10% FCS had a calculated amine metabolic capacity that was 30- to 50-fol d that of the cultured smooth muscle cellular content in a single well of a 96-well plate. Our study demonstrates that SSAO in FCS contributes to amin e metabolism and cytotoxicity to rat cardiovascular cells in vitro and how critical it is to evaluate serum for its role in mechanisms of amine toxici ty in vitro and in vivo. (C) 1998 Society of Toxicology.