Date of Award
Master of Science (MSc)
Tl+ is thought to be toxic to cells due to ionic mimicry of K+. The aims of this study were two-fold. First, to identify whether K+ and Tl+ were interacting in isolated guts, whole animals and tissues in Chironomus riparius, and second, to determine the strategies of Tl+ tolerance. C. riparius. were very tolerant towards Tl+ with a 48-hr LC50 of 723 μmol l-1. The Scanning Ion-selective Technique (SIET) allowed us to identify the caecae, AMG and PMG as the major K+-transporting regions of isolated guts. Evidence for an interaction was based on the finding that Tl+ was transported in the same directions at these segments (and others), and that 50 μmol l-1 Tl+ decreased K+ flux at the AMG and PMG. In addition, exposure to Tl+ prior to flux measurements had significant effects on net K+ transport by the gut. Measurements of Tl+ and K+ concentrations in the whole animal, gut and hemolymph by Atomic Absorption Spectroscopy (AAS) indicated that Tl+ 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+ can perturb K+ transport and homeostasis. The absorption of Tl+ from the gut to hemolymph, measured by SIET, was confirmed by hemolymph measurements of Tl+ using AAS. This indicated that Tl+ gains access to the hemolymph and that sensitive tissues (such as the nervous system) are thus exposed. However, survival of C. riparius at these concentrations implies efficient mechanisms for detoxification of Tl+. 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+ from the muscle may prevent hypokalemia in the hemolymph and gut.
Belowitz, Ryan F. Mr, "INVESTIGATIONS OF THE INTERACTIONS BETWEEN K+ AND Tl+ IN CHIRONOMUS RIPARIUS LARVAE" (2011). Open Access Dissertations and Theses. Paper 6293.
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