Apoptosis in dab (Limanda limanda) as possible new biomarker for anthropogenic stress

Apoptosis, also known as programmed cell death, is a physiological and irreversible process in tissue homeostasis that leads to DNA fragmentation of multiples of 180-200 bp. Because apoptosis can be initiated not only by physiological stimuli but also by various chemical substances, the present paper investigates the suitability of apoptosis as a biomarker for biological effect monitoring in the marine environment. Aquarium experiments with dab (Limanda limanda) were carried out to examine the effects of exposure to cadmium, PCB 118, and PCB 77 (each 1 mg/kg fish wt) on apoptosis in dab liver. Determination of apoptosis was carried out by DNA gel electrophoresis and quantification of DNA fragments smaller than 1500 bp. In addition, accumulated amounts of cadmium, PCB 118, and PCB 77 in dab liver were analyzed. Quantification of the three xenobiotics resulted in an accumulation of about factor 10(2)-10(4). Exposure to PCB 118 and cadmium resulted in an increase in apoptotic DNA fragmentation. Exposure to PCB 77 led mainly to cell death by necrosis.