Cell injury by oxidative stress is an important mechanism for renal epithelial cell destruction. This study observed the protective effect of turmeric and its constituents on H2O2-induced injury. Turmeric consists of a water soluble turmerin and lipid soluble curcumin with potent antioxidant properties. Confluent LLC-PK1 cells were labelled with 3H-arachidonic acid at 0.1 microCi/ml over 18 h and then further labelled with 51Cr. Turmeric ( 100 microg/ml-0.1 microg/ml), turmerin (800 ng/ml-0.8 ng/ml), curcumin (100 microg/ml-0.1 microg/ml), vitamin E (100 microM) and 21-aminosteroid (20 microM) were added and incubated for 3 h at 37 degrees C in 24-well plate. The adherent cells were washed and incubated for 3 h with 1.5 mM H2O2 at 37 degrees C. 3H-arachidonic acid release, 51Cr release and lipid peroxidation by the thiobarbituric acid reaction was determined. Turmeric ( 100 microg/ml) and curcumin (100 microg/ml, 10 microg/ml) gave as much protection as did vitamin E in both chromium release assay and lipid degradation while Turmeric (100 microg/ml) and curcumin (100 microg/ml) gave comparable inhibition of lipid peroxidation. Turmerin and 21-aminosteroid showed no protection. These findings provide evidence that turmeric and curcumin provide protection against oxidative stress in a renal cell line.