<p>Tl<sup>+</sup> is thought to be toxic to cells due to ionic mimicry of K<sup>+</sup>. The aims of this study were two-fold. First, to identify whether K<sup>+</sup> and Tl<sup>+</sup> were interacting in isolated guts, whole animals and tissues in <em>Chironomus riparius, </em>and second, to determine the strategies of Tl<sup>+</sup> tolerance. <em>C. riparius. </em>were very tolerant towards Tl<sup>+ </sup>with a 48-hr LC<sub>50</sub> of 723 μmol l<sup>-1</sup>. The Scanning Ion-selective Technique (SIET) allowed us to identify the caecae, AMG and PMG as the major K<sup>+</sup>-transporting regions of isolated guts. Evidence for an interaction was based on the finding that Tl<sup>+</sup> was transported in the same directions at these segments (and others), and that 50 μmol l<sup>-1 </sup>Tl<sup>+</sup> decreased K<sup>+</sup> flux at the AMG and PMG. In addition, exposure to Tl<sup>+</sup> prior to flux measurements had significant effects on net K<sup>+</sup> transport by the gut. Measurements of Tl<sup>+</sup> and K<sup>+</sup> concentrations in the whole animal, gut and hemolymph by Atomic Absorption Spectroscopy (AAS) indicated that Tl<sup>+</sup> uptake was saturable in the whole animal and gut, and non-saturable in the hemolymph. Together with the SIET measurements, the AAS data suggests that high levels of Tl<sup>+</sup> can perturb K<sup>+</sup> transport and homeostasis. The absorption of Tl<sup>+</sup> from the gut to hemolymph, measured by SIET, was confirmed by hemolymph measurements of Tl<sup>+</sup> using AAS. This indicated that Tl<sup>+</sup> gains access to the hemolymph and that sensitive tissues (such as the nervous system) are thus exposed. However, survival of <em>C. riparius</em> at these concentrations implies efficient mechanisms for detoxification of Tl<sup>+</sup>. This tolerance may involve sequestration in the gut, metal-binding proteins and increased secretion by the anal papillae and MTs. In addition, loss of K<sup>+</sup> from the muscle may prevent hypokalemia in the hemolymph and gut.</p> / Master of Science (MSc)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/11316 |
| Date | 10 1900 |
| Creators | Belowitz, Ryan F. |
| Contributors | O`Donnell, Michael, Wood, Chris, Wood, Chris, Biology |
| Source Sets | McMaster University |
| Detected Language | English |
| Type | thesis |
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