Comparative toxicokinetics of 2,2'- and 4,4'-dichlorobiphenyls in the pond snail Lymnaea stagnalis (L.).

Pond snails (Lymnaea stagnalis (L.)) were treated with 2,2′-dichlorobiphenyl (DCB) or 4,4′-DCB, to examine the toxicokinetic profile of these compounds. Snails were treated orally with 210 μg 4,4′-DCB (impregnated on food) for 14 hr, or snails were injected with 50 μg of 2,2′-DCB or 4,4′-DCB in the foot. At different times after starting feeding or injection, tissues (albumen gland, digestive gland and digestive tube, central nervous system, remainder parts), hemolymph and faeces were analyzed for unchanged 2,2′- or 4,4′-DCB. The results showed that in case of oral administration of 4,4′-DCB after 144 hr, 97.5% of the dose was excreted unchanged in the faeces. During the first 48 hr 4,4′-DCB was found in all tissues. Thereafter, an exponential elimination was found (the rate constant of elimination (kel) varied from 0.010–0.021 per hr, t1/2 from 33–60 hr and the apparent clearance from 0.02–0.3 g/hr for the different tissues). After injection, the compounds were found in all the above mentioned tissues, especially in the digestive gland. There was a clear difference between snails injected with 2,2′- and 4,4′-DCB. Firstly, kel for 2,2′-DCB was higher (0.028 per hr vs 4,4′-DCB: 0.001 per hr). Secondly, 2,2′-DCB was lethal; 63% of the animals died after 72 hr.