|
(70-90) Uptake of waterborne tributyltin in the brain of fish: axonal transport as a mechanism. Xiong, Zhenhu1, Pacepavicius, Grazina2, Rouleau, Claude*,2, 1 Department of civil and environmental engineering, Tianjin, P.R. China2 National Water Research Institute, Burlington, Ontario, Canada ABSTRACT- In previous studies, it was shown that waterborne Hg(II), Cd(II) and Mn(II) enter nerves innervating water-exposed sensory organs of fish and are transported to the brain by axonal transport. However, it is not known if waterborne organometals, such as tributyltin (TBT), can reach the brain of fish via the same route. In this work, we exposed rainbow trout (Oncorhynchus mykiss) to waterborne 113Sn-TBT (4.2 kBq/L). Three fish were sampled after a 2-w exposure, and three others were sampled after a 2-w depuration period. Distribution of 113Sn-TBT was visualized and quantified by quantitative whole-body autoradiography, using a Leica CM3600 cryomicrotome to obtain 20- Key words: tributyltin, fish, axonal transport, whole-body autoradiography |
m-thick cryosections and a Cyclone Phosphor Imager system (Canberra-Packard) for imaging and quantitation. Radioactive TBT was distributed to all the tissues, highest levels being found in the liver (IC = 4-6) (IC = concentration index = concentration in organ / whole-body average concentration), and the lowest levels in the bone (IC = 0.2 to 0.3). The brain accumulated a significant amount of 113Sn-TBT (IC = 1 to 4). Higher levels were found in parts receiving sensory nerves from water-exposed sensory organs, such as eminentia granulares (lateral lines organs), rhombencephalon (gustatory papilla), as well as optic tectum and diencephalon (retina). The olfactory nerve and bulb were also labelled (sensory receptors in olfactory rosette). This specific distribution of TBT in fish brain suggests that this organometal can access the central nervous system via water-exposed sensory nerves. In order to validate the hypothesis of axonal transport, additional work is presently underway to verify the tightness of the blood-brain barrier to TBT. These results will also be presented.