Peroxisome proliferation in the digestive epithelium of mussels exposed to the water accommodated fraction of three oils

Recent studies show that the peroxisomal marker enzyme catalase is induced in the digestive epithelium of mussels exposed to petroleum-derived hydrocarbons. The aim of the present study was to investigate whether this effect is accompanied by a proliferative response of the peroxisomes. Mussels were treated for 21, 49 and 91 days with three different doses of the water accommodated fraction (WAF) of two different crude oils (Ural and Maya types) and of one commercial lubricant oil. The volume density, surface density, surface-to-volume ratio and numerical density of peroxisomes were quantified by stereology on cryostat sections of digestive glands stained for the histochemical demonstration of catalase activity. The results show that after 21 days, the three WAFs act as typical peroxisome proliferators, inducing a significant increase in the volume, surface and numerical densities of peroxisomes in the digestive epithelium. The response is diminished or completely abolished after 49 and 91 days of exposure to the WAFs. The ability to induce the proliferative response differs depending on the WAF type, the lubricant oil showing the maximal induction ability. These results suggest that peroxisome proliferation could be used as a diagnostic biomarker for both exposure and effects of petroleum hydrocarbons on marine biota. (C) 1997 Elsevier Science Inc.