Oxygen radicals production and actin filament disruption in bivalve haemocytes treated with benzo(a)pyrene

Haemocytes play an essential role in the internal defence of molluscs. It has been reported that organic xenobiotics commonly found as pollutants in the marine environment impair defence capabilities of haemocytes. The purpose of the present study was to investigate the effects of benzo(a)pyrene [B(a)P] on the integrity of the actin cytoskeleton and on endocytosis in haemocytes and to see if these effects are related to generation of reactive oxygen species. Haemocytes were exposed in vitro to B(a)P (0.5–40 μg/ml) for 1 h. Cell viability (using 2,3-bis[2-methoxy-4-nitro-5-sulfophenyl]-2H-tetrazolium-5-carboxanilide or XTT assay) indicated that selected doses were sublethal. Uptake of neutral red was significantly decreased in a dose-dependent manner in B(a)P-treated haemocytes. Distribution of actin filaments, labeled with rhodamine-conjugated phalloidin, was altered in haemocytes treated with 20 or 40 μg/ml B(a)P. These effects could be related to an increased production of superoxide anion during B(a)P metabolism, as detected by the nitroblue tetrazolium (NBT) reduction assay in haemocytes treated with 10 μg/ml B(a)P.