In this study, we investigated the mechanism of nitrogen excretion in the soil nematode Caenorhabditis elegans. Utilizing the scanning ion electrode technique (SIET), it was shown for the first time in nematodes that the excretory cell promotes a secretion of ions, including Na+, K+, H+ and Ca2+. In addition, observations from experiments exposing the animal to various environmental pH regimes suggested that the mode of ammonia excretion is dependent on acidification of the unstirred boundary layer, supported also by a detected H+-net-excretion over the hypodermis employing SIET. Pharmacological experiments, SIET and enzyme activity measurements implicated the participation of a functional microtubule network, V-type H+-ATPase, carbonic anhydrase, Na+/K+-ATPase, and apical Na+-channels in the ammonia excretion mechanism of this roundworm. Most importantly, employing ammonia transporter deficient Saccharomyces cerevisiae we were able to show for the first time that an invertebrate Rh-like protein (Rhr-1) does indeed function as an ammonia transporter. Further, a second Rh-protein, Rhr-2, was found to be predominantly expressed in the hypodermis. Knock-out experiments on this transporter further suggested participation of Rhr-2 in the apical ammonia trapping mechanism. Overall, the results of this study provided evidence for a novel ammonia excretion mechanism over the hypodermis, which exhibits features commonly seen in both freshwater (ammonia trapping) and seawater inhabiting species (vesicular transport and exocytosis). / October 2015
| Identifer | oai:union.ndltd.org:MANITOBA/oai:mspace.lib.umanitoba.ca:1993/30721 |
| Date | 15 December 2014 |
| Creators | Aida, Adlimoghaddam |
| Contributors | Dr. Dirk Weihrauch Department o Biological Sciences, Dr. William Diehl Jones Dr. Ann Karen Brassinga Dr. Michele Piercey-Normore |
| Publisher | Journal of experimental biology (JEB) |
| Source Sets | University of Manitoba Canada |
| Detected Language | English |
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