UPTAKE, TISSUE DISTRIBUTION AND METABOLISM OF C-14-LABELED TRIBUTYLTIN (TBT) IN THE DOG-WHELK, NUCELLA-LAPILLUS

A study of tributyltin (TBT) uptake, tissue distribution and breakdown in dog-whelks, Nucella lapillus, was carried out using C-14-labelled tributyltin chloride. The compound was introduced into animals by expo sure to sea-water, from a diet of labelled mussels and by injection. M easurements of C-14 were made on tissue extracts containing total C-14 , TBT+DBT and TBT. Organs examined included digestive gland, kidney, m antle, foot, viscera, gonads and blood. Absorption of dissolved TBT oc curred primarily via tissues associated with the mantle: autoradiograp hic evidence showed that of these the ctenidium (gill) and osphradium were probably most important. Of non-reproductive tissues, mantle disp layed least evidence of TBT degradation whereas kidney and digestive g land contained lower proportions of C-14 as TBT (approximately 60%) th an other tissues. By virtue of its more rapid response, initially at l east, the kidney had a primary role in degrading dissolved TBT that re ached the blood. Dog-whelks feeding on labelled Mytilus edulis absorbe d organotins very efficiently via the digestive gland, which then play ed a major role in TBT breakdown. However, the capacity for degradatio n is not sufficient to prevent, TBT concentration factors of the order of 1 00,000 (dry tissue/water) being attained in N. lapillus. Autorad iography revealed surprisingly high grain-counts in nerves, which may be significant in view of evidence in the literature that neurohormone s are intermediaries in the chain linking TBT with imposex.