Effects of flavonoids on stress response of myotube cultures was studied by monitoring the release of [14C] taurine, leukotriene production, and 2',7'-dichlorodihydroflourescein (DCFH2) oxidation. Stress was induced by hypotonic shock, which was accompanied by cell swelling leading to increased leukotriene production and a concomitant increase in reactive oxygen species and osmolyte release. In this model system, addition of the flavonoids catechin and quercetin decreased leukotriene production, DCFH2 oxidation, and taurine efflux, indicating a reduction of cellular stress. High concentrations of epigallocatechin gallate (EGCG) and tea extract increased leukotriene production and initial DCFH2 oxidation, indicating an increased cellular stress (possibly toxicity). However, taurine efflux was reduced, and also longer exposure time as well as lower concentrations of EGCG and tea reduced DCFH2 oxidation. Trolox and alpha-tocopherol did not significantly affect taurine efflux or leukotriene production, and it was therefore concluded that suppression of these responses was not confined to redox activity in a myotube culture.